Methioninase: a therapeutic for diseases related to altered methionine
metabolism and transmethylation: cancer, heart disease, obesity, aging, and Parkinson's
disease.
"Disruption and abnormalities in methionine
metabolism and transmethylation seems to be associated with the major diseases of mankind,
including cancer, heart disease, aging, obesity, and Parkinson's disease."
Mechanisms and consequences of the impaired trans-sulphuration pathway in
liver disease: Part II. Clinical consequences and potential for pharmacological
intervention in cirrhosis.
"The liver is actively involved in the metabolism of the
sulphur-containing essential amino acid, methionine. Methionine is transformed into S-adenosyl-L-methionine (SAMe) and
then into sulphur-containing metabolites (cysteine, taurine and glutathione) via the
trans-sulphuration pathway."
The number of scientific studies of methinone
is vast!
"The literature on sulfur amino acid metabolism is too vast for a short
chapter to cover in great depth. I attempt here a brief overview with references to many
specialized review articles. This review emphasizes aspects of sulfur amino acid
metabolism elucidated in the last ten years, in particular aspects not generally covered
in biochemistry texts, e.g. transaminative pathways of methionine metabolism."
Isolation of the murine S100 protein MRP14 (14 kDa
migration-inhibitory-factor-related protein) from activated spleen cells: characterization
of post-translational modifications and zinc binding.
Treatment of nude mice with 4-amidinoindan -1- one2 '- amidinohydrazone, a
new S-adenosylmethionine decarboxylase inhibitor, delays growth and inhibits metastasis of
human melanoma cells.
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The biochemistry of endogenous organosulphur compounds.
Author
James SP
Address
School of Biochemistry, University of Birmingham, UK.
Source
Drug Metabol Drug Interact, 1988, 6:3-4, 167-82
Abstract
The role and metabolism of methionine and cysteine in
mammals are described. An outline of the history of glutathione, of its function in
maintaining the thiol status of the cell and of its protective action against oxidative
stress, is given. The importance of glutathione reductase, glutathione peroxidases,
glutathione-S-transferases in endogenous metabolism and of gamma-glutamyltranspeptidase is
described. The relationship between cysteine and glutathione is considered together with
the inter-organ translocation of glutathione and its metabolism.
Methioninase: a therapeutic for diseases related to altered methionine
metabolism and transmethylation: cancer, heart disease, obesity, aging, and Parkinson's
disease.
Author
Hoffman RM
Address
AntiCancer, Incorporated, San Diego, CA 92111, USA. all@anticancer.com
Source
Hum Cell, 1997 Mar, 10:1, 69-80
Abstract
Methionine metabolism and transmethylation are central to
the metabolism and differentiation of all known cells. In enkaryotic organisms, methionine metabolism and transmethylation are of paramount
importance in modification and regulation of proteins, lipids, and nucleic acids. The
differential methylation of genes regulates their expression in the myriad of cells in
eukaryotic organisms. Disruption and abnormalities in methionine
metabolism and transmethylation seems to be associated with the major diseases of mankind,
including cancer, heart disease, aging, obesity, and Parkinson's disease. In this review,
we describe how aberrant and abnormal methionine metabolism
and transmethylation are related to these major diseases. Most importantly, we review and
hypothesize how the developing therapeutic recombination methioninase (rMETase) can be
utilized to cure or prevent all of these diseases.
Recent experimental evidence links changes in methionine
metabolism to the onset and progression of cancer. Aberrant methylation reactions and
polyamine synthesis may alter genome stability, gene expression, and cell proliferation.
Language of Publication
English
Unique Identifier
94013160
MeSH Heading (Major)
Methionine|*ME; Neoplasms|DI/*ET/ME
MeSH Heading
Cell Transformation, Neoplastic|ME; DNA Damage; DNA Repair; Human; Oncogene Proteins|ME
Methionine sulfoxide and the oxidative regulation of plasma
proteinase inhibitors.
Author
Swaim MW; Pizzo SV
Address
Department of Pathology, Duke University Medical Center, Durham, North Carolina 27710.
Source
J Leukoc Biol, 1988 Apr, 43:4, 365-79
Abstract
The sensitivity of methionine residues to oxidation is a
mechanism by which many proteins, including plasma proteinase inhibitors, may be
oxidatively inactivated. Much evidence suggests that methionine
oxidation and concurrent losses of protein activity not only occur widely in living
systems but are physiologic, homeostatic processes. Neutrophils, macrophages and other
leukocytes secrete large quantities of powerful oxidants at sites of inflammation and may
readily bring about methionine oxidative inactivation of
proteins. In particular, oxidation of proteinase inhibitors may favorably alter the
proteinase-antiproteinase balance to facilitate tissue remodeling and protection from
invading organisms. Leukocyte-mediated inhibitor oxidation also appears to regulate local
immunosuppressive activity. Pathophysiologic processes such as emphysema and rheumatoidal
disease involve derangements of these homeostatic mechanisms.
Department of Neurosurgery, Osaka City University Medical School, Japan.
Source
J Comput Assist Tomogr, 1997 Jul-Aug, 21:4, 590-3
Abstract
A 43-year-old woman was admitted with a tumor mass in her forehead. Two months
previously, a lump in her breast had been diagnosed as mastopathy. Palpation revealed an
elastically hard immobile tumor mass in her forehead. MRI detected a tumoral lesion of
generally uniform contrast involving frontal subcutaneous, cranial, and intracranial
regions. PET demonstrated more intensive and wider accumulation of [11C]methyl-L-methionine (Met) than of [18F]fluoro-2-deoxyglucose (FDG). Biopsy
of the forehead mass was performed, which was diagnosed as B-cell-type malignant lymphoma.
The tumor mass in the forehead then shrank spontaneously, as confirmed by palpation and
MRI. The tumor mass in the left breast was totally extirpated and histologically diagnosed
as B-cell-type malignant lymphoma, like the tumor mass in the forehead. Postoperatively,
chemotherapy (VEPA) was performed. Although FDG accumulation had not been detected,
postchemotherapy PET demonstrated slight Met accumulation, suggesting the presence of a
residual tumor. PET served well to detect the lesion and evaluate therapeutic efficacy in
malignant lymphoma. Met-PET was more sensitive to malignant lymphoma than FDG-PET.
Functional methionine synthase deficiency (cblE and cblG):
clinical and biochemical heterogeneity.
Author
Watkins D; Rosenblatt DS
Address
Centre for Human Genetics, McGill University, Montreal, Quebec, Canada.
Source
Am J Med Genet, 1989 Nov, 34:3, 427-34
Abstract
Functional methionine synthase deficiency is generally
characterized by homocystinuria and hypomethioninemia in the absence of methylmalonic
aciduria. Patients are divided into two classes, cblE and cblG, on the basis of
complementation analysis. Presentation has usually been in the first 2 years of life, but
one patient came to medical attention at age 21 years with symptoms initially diagnosed as
multiple sclerosis. Common findings among 11 patients (4 with cblE and 7 with cblG) have
included megaloblastic anemia (all patients) and various neurological deficits including
developmental retardation (10 patients), cerebral atrophy (8 patients), hypotonia (7
patients), EEG abnormalities (6 patients), and nystagmus (5 patients). Hypertonia,
seizures, blindness, and ataxia were less frequent. All patients have responded to therapy
with cobalamin with resolution of anemia and biochemical abnormalities; neurological
deficits resolved more slowly and in some cases incompletely. Hydroxycobalamin has been
more effective than cyanocobalamin. Fibroblasts from patients with cblE (5 patients) and
cblG (6 patients) all showed decreased intracellular levels of methylcobalamin (MeCbl) and
decreased incorporation of label from 5-methyltetrahydrofolate into macromolecules,
suggesting decreased activity of the MeCbl-dependent enzyme methionine
synthase. Methionine synthase specific activity in extracts
of all cblE fibroblasts was normal or near-normal under standard reducing conditions;
synthase specific activity in extracts of 5 cblG patients was low but was high in a 6th
patient measured in another laboratory. Thus, there is heterogeneity among patients with
functional methionine synthase deficiency both in clinical
presentation and in the results of biochemical studies of cultured cells.
Language of Publication
English
Unique Identifier
90086914
MeSH Heading (Major)
Homocystinuria|*EN/GE; Methionine|BL/*DF;
Methyltransferases|*DF; Tetrahydropteroylglutamate Methyltransferase|*DF/GE; Vitamin B
12|*AA/BL/TU
Plasma homocysteine and methionine tolerance in early-onset
vascular disease.
Author
Brattström L; Israelsson B; Hultberg B
Address
Department of Neurology, University Hospital, Lund, Sweden.
Source
Haemostasis, 1989, 19 Suppl 1:, 35-44
Abstract
In three different studies we tested the hypothesis that early-onset vascular disease is
associated with impaired homocysteine metabolism which could contribute to the development
of arteriosclerosis and thrombosis. In patients with occlusive vascular disease before the
age of 60, a post-methionine load increase of plasma
homocysteine exceeding the highest value for comparable healthy control subjects was found
in 1 of 21 with myocardial infarction (5%), 14 of 37 with aorto-iliac disease (38%), and
17 of 53 with cerebrovascular disease (32%). This might indicate heterozygosity for
homocystinuria due to cystathionine beta-synthase deficiency. Concentrations of serum
vitamin B12 and red cell folate had an important modulating effect on plasma homocysteine
concentrations in the fasting state.
The influence of ethanol on hepatic transmethylation.
Author
Barak AJ; Beckenhauer HC
Address
Liver Study Unit, Veterans Administration Medical Center, Omaha, NE 68105.
Source
Alcohol Alcohol, 1988, 23:1, 73-7
Abstract
One of the most important biochemical pathways in the organism is the biosynthesis of methionine from the methylation of homocysteine. Two different
reactions are responsible for this methylation, one utilizing N5-methyltetra-hydrofolate
as a methylating agent and the other using betaine as the methyl donor. This paper reviews
some recent findings in this laboratory, which demonstrate that ethanol-feeding to rats
impairs the folate-induced reaction. Our findings also show that this impairment is
compensated for through the adaptive increase in the enzyme using betaine in the
biosynthesis of methionine. Further studies indicate that the
mechanism of action in the impairment may occur through the formation of individual
adducts between the folate-induced enzyme (methionine
synthetase), its essential cofactors and acetaldehyde, a metabolic product of ethanol.
These findings suggest a basis for why rats are more resistant to alcoholic liver injury
than humans and may offer a means of protecting against alcoholic liver injury in man.
Slowed synthesis of DNA and methionine is a pathogenetic
mechanism common to dementia in Down's syndrome, AIDS and Alzheimer's disease?
Author
Regland B; Gottfries CG
Address
Department of Geriatrics and Rehabilitation, Uddevalla Hospital, Rosenhäll, Sweden.
Source
Med Hypotheses, 1992 May, 38:1, 11-9
Abstract
This is a presentation of the hypothesis of a pathogenetic mechanism common to the
dementia seen in Alzheimer's disease (AD), Down's Syndrome (DS) and the acquired
immunodeficiency syndrome (AIDS). As there is experimental evidence of defective DNA
repair capacity in AD and DS, unrepaired damage to DNA occurs in these diseases and may
lead to complete breakdown of cellular function and ultimate cell death. Cobalamin and
folate are coordinated in a vulnerable key position in the synthesis of DNA and
S-adenosylmethionine (SAM). Cobalamin/folate deficiency, a significant feature in senile
dementia of Alzheimer type and in AIDS-related dementia complex, will result in
concomitant slowed synthesis of DNA and SAM. The enzyme cystathionine-beta-synthetase
(CBS) has been localized to the chromosome band 21q22.3. Owing to gene dosage, CBS
activity is increased in trisomy 21. As a consequence, cobalamin/folate metabolism is
inhibited, which leads to slowing of DNA and SAM synthesis in DS patients. Amyloidosis is
a hallmark of AD and DS brain neuropathology and recent experimental findings support the
view that amyloid or amyloid precursors stimulate DNA synthesis, which is in agreement
with the hypothesis presented in this paper. In summary, demented patients with
cobalamin/folate deficiency, trisomy 21 and human immunodeficiency virus (HIV) infection
display a simultaneous downregulation of DNA and SAM synthesis, which may indicate a
pathway common to the dementia seen in AD, DS and AIDS.
Language of Publication
English
Unique Identifier
92310301
MeSH Heading (Major)
Alzheimer's Disease|PA/*PP; AIDS Dementia Complex|PA/*PP; Dementia|ET/PA/*PP; Down
Syndrome|PA/*PP; DNA|*BI; Methionine|*BI
MeSH Heading
Amyloidosis|ET/PA/PP; Cell Death; DNA Repair; DNA Replication; Human; Models, Biological
Methionine deprivation regulates the translation of
functionally-distinct c-Myc proteins.
Author
Hann SR
Address
Department of Cell Biology, Vanderbilt Univeristy, School of Medicine, Nashville,
Tennessee 37232-2175, USA.
Source
Adv Exp Med Biol, 1995, 375:, 107-16
Abstract
Numerous studies have demonstrated a critical role for the c-myc gene in the control of
cellular growth. Alterations of the c-myc gene have been found associated with many
different types of tumors in several species, including humans. The increased synthesis of
one of the major forms of c-Myc protein, c-Myc 1, upon methionine
deprivation provides a link between the regulation of oncogenes and the nutritional status
of the cell. While deregulation or overexpression of the other major form, c-Myc 2, has
been shown to cause tumorigenesis, the synthesis of c-Myc 1 protein is lost in many
tumors. This suggests that the c-Myc 1 protein is necessary to keep the c-Myc 2 protein
"in check" and prevent certain cells from becoming tumorigenic. Indeed, we have
shown that overproduction of c-Myc 1 can inhibit cell growth. We have also shown that
c-Myc 1 and 2 proteins have a differential molecular function in the regulation of
transcription through a new binding site of Myc/Max heterodimers. We have also recently
identified new translational forms of the c-Myc protein which we term delta-c-Myc. These
proteins arise from translational initiation at downstream start sites which yield
N-terminally-truncated c-Myc proteins. Since these proteins lack a significant portion of
the transactivation domain of c-Myc, they behave as dominant-negative inhibitors of the
full-length c-Myc 1 and 2 proteins. The synthesis of delta-c-Myc proteins is also
regulated during cell growth and is repressed by methionine
deprivation. Therefore, the synthesis of c-Myc 1 and delta-c-Myc proteins are reciprocally
regulated by methionine availability. We have also found some
tumor cell lines which synthesize high levels of the delta-c-Myc proteins. Taken together,
our data suggest that c-Myc function is dependent on the levels of these different
translational forms of c-Myc protein which are regulated by the nutritional status of the
cell during growth. Numerous reports have demonstrated a fundamental and diverse role for
the myc gene in cellular events, including proliferation, differentiation and apoptosis
(Cole 1986; Spencer and Groudine 1991; Askew et al. 1991; Evan et al. 1992). This is
dramatically illustrated by the frequent occurrence of a variety of tumors in many species
having alterations of myc genes and the transduction of c-myc sequences by retroviruses
(Spencer and Groudine 1991).4+ Eisenman 1990).(ABSTRACT TRUNCATED AT 400 WORDS)
Instituto de Investigaciones Biomédicas, CSIC, Madrid, Spain.
Source
Adv Exp Med Biol, 1994, 368:, 113-7
Abstract
Methionine metabolism impairment in human liver disease has
been related with an alteration in SAM-synthetase. This deficiency is produced by a
post-translational event since human liver cirrhosis presents normal levels of
SAM-synthetase mRNA in spite of a more than 50% diminution in its activity. A series of
different experiments on the structure and activity of this enzyme have provided strong
evidence that SAM-synthetase is regulated by reduced/oxidized glutathione ratio.
Restoration of glutathione levels by the addition of S-adenosyl-methionine or glutathione
esters in various experimental conditions (buthionine sulfoximine and carbon tetrachloride
intoxication) resulted in a normalization of the SAM-synthetase diminution caused by the
toxics and an attenuation of the morfological alteration produced in the liver, including
fiber production. This findings might have pharmacological implications in the treatment
of liver diseases, since the possible beneficial effect of long term administration of SAM
could include a reduction of fiber production.
Oxidation of methionyl residues in proteins: tools, targets, and reversal.
Author
Vogt W
Address
Max Planck Institut für experimentelle Medizin, Göttingen, Germany.
Source
Free Radic Biol Med, 1995 Jan, 18:1, 93-105
Abstract
Methionine (Met) is one of the most readily oxidized amino
acid constituents of proteins. It is attacked by H2O2, hydroxyl radicals, hypochlorite,
chloramines, and peroxynitrite, all these oxidants being produced in biological systems.
The oxidation product, Met sulfoxide, can be reduced back to Met by Met sulfoxide
reductase. Numerous proteins lose functional activity by Met oxidation. However,
functional activation of proteins by Met oxidation has also been observed. Functional
changes by Met oxidation in a given protein appear to have pathophysiological significance
in some cases. Considering the reversibility of Met oxidation and the functional changes
associated with the oxidation, it seems possible that Met oxidation/reduction in proteins
may be one means to control homeostasis in biological systems.
Methyl donors in the diet and responses to chemical carcinogens.
Author
Rogers AE
Address
Boston University School of Medicine, Department of Pathology and Laboratory Medicine,
Mallory Institute of Pathology, MA 02118.
Source
Am J Clin Nutr, 1995 Mar, 61:3 Suppl, 659S-665S
Abstract
Dietary deficiency of labile methyl donors (choline and methionine)
increases spontaneous and chemically induced hepatocarcinogenesis in rats. Chemical
carcinogenesis in the colon, mammary gland, esophagus, and pancreas also may be increased.
The mechanism of the dietary effect is not known but may be related to reduced methylation
of DNA and RNA, hyperplasia of target cells, increased peroxidative damage, and altered
carcinogen or promoter metabolism. Folate deficiency also is associated with increased
carcinogenesis, an effect that may be mediated through participation in methyl metabolism;
this has been less extensively studied. Deficiency of these three nutrients also may play
a role in the elevated cancer risk in humans that is associated with ethanol intake.
Mechanisms and consequences of the impaired trans-sulphuration pathway in liver disease:
Part II. Clinical consequences and potential for pharmacological intervention in
cirrhosis.
Author
Pisi E; Marchesini G
Address
Istituto di Clinica Medica Generale e Terapia Medica, Università di Bologna, Italy.
Source
Drugs, 1990, 40 Suppl 3:, 65-72
Abstract
The liver is actively involved in the metabolism of the sulphur-containing essential
amino acid, methionine. Methionine
is transformed into S-adenosyl-L-methionine (SAMe) and then into sulphur-containing
metabolites (cysteine, taurine and glutathione) via the trans-sulphuration pathway. Liver
disease may affect the trans-sulphuration pathway and decrease the clearance of methionine, which leads to increased fasting methionine
concentrations in blood and reduced formation of cysteine and glutathione. There is
evidence that this defect, located at the level of SAMe-synthetase, may cause nutritional
defects and contribute to negative nitrogen balance whenever non-essential
sulphur-containing amino acids are not supplied in adequate amounts. In addition,
cirrhotic patients may be at increased risk of hepatotoxicity after treatment with
substances which are detoxified via glutathione. The SAMe-synthetase block may be overcome
by administration of oral or intravenous SAMe, which improves the fasting amino acid
profile and increases the hepatic glutathione concentration. Controlled studies on long
term SAMe treatment in patients with cirrhosis are needed to confirm this possible
beneficial effect.
Departamento de Metabolismo, Nutrición y Hormonas, Fundación Jiménez Diaz, Madrid,
Spain.
Source
Drugs, 1990, 40 Suppl 3:, 58-64
Abstract
The energy-dependent conversion of methionine to S-adenosyl-L-methionine (SAMe) is
catalysed by S-adenosyl-L-methionine synthetase (SAMe-synthetase) in the liver. In the
hepatocyte, an equilibrium exists between the high and low molecular weight forms of
SAMe-synthetase, which consist of a tetramer and a dimer, respectively, of a 48.5
kilodalton subunit. The 2 enzymic forms differ in their affinity for methionine and
sensitivity to inhibition by pyrophosphate; 2 of the sulfhydryl groups of SAMe-synthetase
have been identified as essential for the normal functioning of the enzyme. In patients
with liver cirrhosis, a marked reduction in the utilisation of the high molecular weight
SAMe-synthetase and displacement of the equilibrium occur, the molecular mechanism of
which has yet to be established. This loss of activity is associated with a delay in
methionine clearance and impairment of the trans-sulphuration pathway, which normally
eliminates excess methionine by oxidising homocysteine to sulphate anion. It is
hypothesised that in normal liver function the essential sulfhydryl groups of
SAMe-synthetase are protected from oxidation by glutathione, a by-product of the
trans-sulphuration pathway. However, glutathione levels are reduced in liver cirrhosis,
and this may result in increased oxidation of the essential sulfhydryl groups, and
consequent inactivation of the enzyme. Thus, the trans-sulphuration pathway may play an
important role in the maintenance of normal SAMe-synthetase activity.
Chemoattractant receptor affinity reflects its ability to transduce different biological
responses.
Author
Snyderman R
Source
Agents Actions Suppl, 1983, 12:, 323-36
Abstract
The oligopeptide chemotactic factor receptor in human PMN membranes exists in two
affinity states which are in part interconvertible and regulated by guanine nucleotides.
In whole cells, only one affinity of the receptor can be seen, presumably due to the high
intracellular levels of guanine nucleotides as well as rapidly ongoing cellular processes
which allow the detection of only a single affinity state. There is strong evidence to
suggest that the affinity of the chemoattractant receptor in whole PMNs can be modified by
agents which alter the physical state of the PMN membrane. The average affinity of the
oligopeptide chemotactic factor receptor can be enhanced by aliphatic alcohols which
decrease membrane microviscosity. Under these conditions, chemotactic responsiveness of
PMNs is enhanced but 0(2-) production and secretion initiated by chemoattractants is
markedly depressed. When the affinity of the receptor is lowered as in the case of
amphotericin B, chemotaxis is depressed but lysozyme secretion is enhanced. These data
indicate that the transduction mechanisms for certain biological responses initiated by
the chemoattractant receptor are heterogeneous. It can be hypothesized that the particular
transduction pathway initiated by chemoattractant receptor occupancy is reflected by the
affinity state of the receptor. The higher affinity state initiates chemotactic signals
whereas the lower affinity state initiates 0(2-) production and secretion. By altering the
affinity of the receptor using pharmacological means one may be able to modify the
biological activity of human PMNs.
Dynamics of human neutrophil receptors for the chemoattractant fmet-leu-phe.
Author
Gallin JI; Seligmann BE; Fletcher MP
Source
Agents Actions Suppl, 1983, 12:, 290-308
Abstract
Neutrophils contain an intracellular pool of binding sites for the chemoattractant
fmet-leu-phe with the same density as specific granules. This pool of receptors appears to
be translocated to the plasma membrane during degranulation and may be important for
receptor renewal during chemotaxis. Scatchard analyses of fmet-leu-phe binding to
neutrophils and isolated plasma membranes are nonlinear and calculated Hill coefficients
of binding to these fractions were about 0.67, suggesting negative cooperativity and/or
heterogeneity of receptors. Some of the features of the nonlinear Scatchard curves may
reflect heterogeneity of binding among cells since binding of fmet-leu-phe-lys-fluorescein
to cells is heterogeneous when simultaneously monitored in the fluorescence activated cell
sorter with a fluorescent probe of membrane potential. Following addition of a
chemoattractant cells showing a depolarization have more chemoattractant associated with
them than cells showing no change of membrane potential or a hyperpolarization. The cell
associated chemoattractant is largely in a displaceable pool on the cells showing
depolarization while it is in a nondisplaceable pool in the cells that either do not
respond or show a hyperpolarization. Studies of the adaptation of human neutrophils
responsiveness to fmet-leu-phe elicited membrane potential changes indicate that
fmet-leu-phe stimulated decreases in receptor affinity accompany such adaptation. This
decreased affinity appears to involve heterogeneity and/or negative cooperative
interaction of receptors. The dynamics of chemoattractant receptors that have been
reviewed provide further insights for studying the concepts behind the spatial and
temporal mechanisms by which cells respond and adapt to a gradient of chemoattractant.
The literature on sulfur amino acid metabolism is too vast for a short chapter to cover
in great depth. I attempt here a brief overview with references to many specialized review
articles. This review emphasizes aspects of sulfur amino acid metabolism elucidated in the
last ten years, in particular aspects not generally covered in biochemistry texts, e.g.
transaminative pathways of methionine metabolism. A selected list of reviews is given in
references 1-15. References to reviews on glutathione are covered in the chapter by A.
Meister in this volume (1a).
Diseases of sulphur metabolism: implications for the methionine-homocysteine cycle, and
vitamin responsiveness.
Author
Mudd SH
Source
Ciba Found Symp, 1979, :72, 239-58
Abstract
Sixteen inherited human diseases are now recognized, affecting most of the major steps
in sulphur metabolism. Studies of patients with three types of homocystinuria have
demonstrated unequivocally the major role of cystathionine formation in degradation of
homocysteine, and the importance of homocysteine remethylation. Methionine balance studies
of normal subjects and of a sarcosine oxidase-deficient subject have shown the predominant
role of creatine synthesis in methionine utilization and permitted assessment of the rate
of oxidation of the methyl group of methionine. Together, the results demonstrate that
once regulatory adjustments have been made the rate of methylneogensis is nicely
controlled so that labile methyl groups are made available in amounts just sufficient to
meet the needs for methionine. When excess methionine is ingested the four-carbon moiety
is diverted into cystathionine, the methyl group is oxidized via sarcosine and the flow of
partially oxidized one-carbon units is diverted away from 5-methyltetrahydrofolate toward
CO2. Studies of cystathionine synthase-deficient patients demonstrate that the capacity to
respond or not to respond to pyridoxine administration is genetically controlled, probably
through structural differences in mutant cystathionine synthases. However, the properties
of the enzyme crucial in conferring responsiveness have not yet been identified.
Transmethylation hypothesis of schizophrenia: methionine
and nicotinic acid.
Author
Nestoros JN; Ban TA; Lehmann HE
Source
Int Pharmacopsychiatry, 1977, 12:4, 215-46
Abstract
The transmethylation hypothesis of schizophrenia was reviewed with considerations that
large doses of methionine when combined with a monoamine
oxidase inhibitor lead to exacerbation of psychotic symptoms in a significant percentage
of chronic schizophrenic patients. It was noted that nicotinic acid in the dosage of 3,000
mg/day can neither prevent nor counteract the psychopathology thus induced.
Effects on transmethylation by high-dose 6-mercaptopurine and methotrexate infusions
during consolidation treatment of acute lymphoblastic leukemia.
Author
Keuzenkamp-Jansen CW; De Abreu RA; Blom HJ; Bökkerink JP; Trijbels JM
Address
Laboratory of Pediatrics, University Hospital St. Radboud, Nijmegen, The Netherlands.
Source
Biochem Pharmacol, 1996 May 3, 51:9, 1165-71
Abstract
6-mercaptopurine (6MP) cytotoxicity is caused by thioguanine and methylthioinosine
nucleotides. Thiopurine methylation occurs to a large extent in vivo and in vitro. In this
reaction, S-adenosyl-L-methionine (AdoMet), produced from
and ATP, is converted into S-adenosyl-L-homocysteine (AdoHcy) which, in turn, is
hydrolyzed into homocysteine. Remethylation of homocysteine into methionine
is inhibited by methotrexate (MTX). In cultured lymphoblasts, AdoMet: AdoHcy ratio and DNA
methylation decrease after incubation with 6MP. The aim of the present study was to
investigate the influence of high-dose 6MP on the methylation capacity in children with
acute lymphoblastic leukemia. Five patients received 4 courses with high-dose intravenous
MTX (5' g.m-2 in 24 hr) immediately followed by high-dose 6MP (1300 mg.m-2 in 24 hr). Five
control patients received high-dose MTX and oral 6MP (25 mg.m -2 daily for 8 weeks).
Leucovorin rescue was started at 36 hr in both groups. In the intravenous 6MP group,
6-methylmercaptopurine, its riboside, and 6-methylmercapto-8-hydroxypurine were detectable
in plasma in concentrations of 0.3-2.6 muM (6MP steady state levels: 11.6 muM). In red
blood cells, mean methylthioinosine nucleotide levels were one third of those of ATP (13.1
nmol/10(8)). AdoHcy levels (10 pmol/10(8)) remained constant in both groups and AdoMet was
not detectable ( < 20 pmol/10(8)). In both groups, plasma homocysteine increased and
decreased following administration of MTX. The delay in the recovery of methionine in the intravenous 6MP group after MTX infusion is
probably the result of an increased demand on methyl groups during 6MP infusion.
Isolation of the murine S100 protein MRP14 (14 kDa migration-inhibitory-factor-related
protein) from activated spleen cells: characterization of post-translational modifications
and zinc binding.
Author
Raftery MJ; Harrison CA; Alewood P; Jones A; Geczy CL
Address
Immunology Group, Heart Research Institute, Camperdown, New South Wales, Australia.
Source
Biochem J, 1996 May 15, 316 ( Pt 1):, 285-93
Abstract
MRP14 (macrophage migration-inhibitory factor-related protein of molecular mass 14 kDa)
is an S100 calcium binding protein constitutively expressed in human neutrophils which may
be associated with cellular activation/inflammation. Murine MRP14 expression was
up-regulated following concanavalin A activation of spleen cells, and the protein was
isolated from conditioned medium in high yield (approx. 500 ng/ml). MRP14 had a mass of
12972 +/- 2 Da by electrospray ionization MS, whereas the theoretical mass derived from
the cDNA sequence, after removal of the initiator Met, was 12918 Da, suggesting that the
protein was post-translationally modified. We identified four post-translational
modifications of MRP14: removal of the N-terminal Met, N-terminal acetylation, disulphide
bond formation between Cys79 and Cys90, and 1-methylation of His106; the calculated mass
was then 12971.8 Da. Methylation of His106 was further characterized after incubation of
spleen cells with L-[methyl-3H]Met during concanavalin A stimulation. Sequential analysis
of a peptide (obtained by digestion with Lys C) containing methylated His indicated that
> 80% of the label in the cycle corresponded to His106, suggesting that the methyl
residue was transferred from S-adenosyl-L-methionine. Comparison of the C18 reverse-phase
HPLC retention times of phenylthiocarbamoyl derivatives of a hydrolysed digest peptide of
MRP14 with those of standards confirmed methyl substitution on the 1-position of the
imidazole ring. MRP14 bound more 85Zn2+ than the same amounts of the 10 kDa chemotactic
protein (CP10) or S100 beta. Ca2+ decreased Zn2+ binding in S100 beta but it did not
influence binding to MRP14, suggesting that the Zn2+ binding site was distinct from and
independent of the two Ca2+ binding domains.
Metabolic Unit, University Children's Hospital Basel, Switzerland.
Source
Clin Sci (Colch), 1996 Jul, 91:1, 79-86
Abstract
1. Elevated plasma homocysteine concentration, either in the fasting state or after methionine loading, is an independent risk factor for vascular
disease in man. Methionine loading has been used to
investigate impaired methionine metabolism, especially of the
trans-sulphuration pathway, but most studies have focused on changes in homocysteine. 2.
We investigated the effect of methionine excess on total
plasma homocysteine, 5-methyltetrahydrofolate (which is the active form of folate in the
remethylation of homocysteine to methionine),
S-adenosyl-methionine (the first metabolite of methionine)
and S-adenosylmethionine) (the demethylated product of S-adenosylmethionine) over 24h in
12 healthy subjects. 3. As well as the expected increase in homocysteine (from 8.0 +/- 1.3
to 32.6 +/- 10.3 mumol/l, mean +/- SD, P < 0.001), S-adenosylmethionine showed a
significant transient increase (from 37.9 +/- 25.0 to 240.3 +/- 109.2 nmol/l, P <
0.001), which correlated well with homocysteine (r2 = 0.92, P < 0.001).
5-Methyltetrahydrofolate values decreased significantly (from 23.2 +/- 7.2 to 13.1 +/- 2.9
nmol/l, P < 0.01), and gradually returned to baseline levels after 24h. No significant
change over the time of measurement was found for S-adenosylhomocysteine. 4. The sequence
of metabolic changes observed in this study strongly suggests that a change in either
homocysteine or S-adenosylmethionine may cause a reduction in 5-methyltetrahydrofolate.
This must be considered in evaluating the relationship between folate and homocysteine in
vascular disease. The metabolic relationships illustrated in this study should be
evaluated in the search for pathogenetic mechanisms of mild hyperhomocysteinaemia and
vascular disease.
DNA hypomethylation and proliferative activity are increased in the rectal mucosa of
patients with long-standing ulcerative colitis.
Author
Glória L; Cravo M; Pinto A; de Sousa LS; Chaves P; Leitão CN; Quina M; Mira FC; Soares
J
Address
Servico de Gastrenterologia, Instituto Português de Oncologia Francisco Gentil de
Lisboa, Portugal.
Source
Cancer, 1996 Dec 1, 78:11, 2300-6
Abstract
BACKGROUND: DNA methylation and DNA cytometric parameters were evaluated in the rectal
mucosa from patients with extensive and long-standing ulcerative colitis. METHODS:
Twenty-six patients with extensive disease for more than 7 years and 11 healthy controls
were included. Global DNA methylation was assessed as the capacity of the DNA test to
incorporate [3H]methyl groups from [3H]-S-adenosyl-methionine in the presence of Sss1
methylase. A higher incorporation reflects a lower state of intrinsic methylation. DNA
ploidy, S-phase fraction, and proliferative index (PI = S + G2M) of the cell cycle were
analyzed by flow cytometry. RESULTS: Incorporation of the [3H]methyl groups into DNA was
10-fold higher in patients compared with controls (P < 0.001) and was significantly
higher in patients with histologically active disease (P = 0.02). With regard to flow
cytometry, all samples showed a diploid pattern, but S-phase fraction and the
proliferative index values were significantly increased in patients compared with controls
(P = 0.0007 and P = 0.003, respectively). A positive correlation was found between S-phase
fraction and proliferative index and the number of exacerbations of the disease (P <
0.005), and there was a trend among those patients who had disease for longer than 20
years to present with increased cellular proliferation compared with those with a shorter
evolution of disease (P > 0.05). CONCLUSIONS: DNA hypomethylation and proliferative
activity are increased in this group of patients, supporting the concept that their
colonic mucosa undergoes epigenetic and kinetic changes that might predispose these
individuals to develop colorectal neoplasms. However, it cannot be ruled out that these
markers solely reflect hyperproliferation associated with active inflammation.
In vitro effects of methotrexate on polyamine levels in lymphocytes from rheumatoid
arthritis patients.
Author
Nesher G; Osborn TG; Moore TL
Address
Department of Internal Medicine, Saint Louis University Health Sciences Center, Missouri
63104, USA.
Source
Clin Exp Rheumatol, 1996 Jul-Aug, 14:4, 395-9
Abstract
OBJECTIVE: Several studies have documented increased levels of polyamines in rheumatoid
arthritis (RA). We have suggested that one of the mechanisms of action of methotrexate
(MTX) involves the inhibition of polyamine synthesis in lymphocytes. In this study, we
sought to establish the inhibitory effect of MTX on polyamine synthesis and its
specificity. METHODS: Polyamine levels were determined in stimulated RA lymphocytes
incubated in vitro with MTX and compared to levels in lymphocytes incubated with
hydrocortisone, D-penicillamine, or medium alone. Lymphocyte polyamine levels were
correlated with IgM-rheumatoid factor (RF) synthesis. RESULTS: Incubation with MTX
resulted in concentration-dependent decreased intracellular levels of spermidine and
spermine, while putrescine levels were not affected. Addition of folinic acid or
S-adenosyl-methionine (SAM) prevented this MTX-induced inhibition. Incubation with
D-penicillamine or hydrocortisone had no significant effect on polyamine levels. There was
a positive correlation between intracellular polyamine levels and the inhibition of IgM-RF
synthesis by MTX. CONCLUSION: These data suggest that MTX inhibits the synthesis of
spermidine and spermine in stimulated RA lymphocytes through inhibition of the
SAM-dependent pathway. This inhibition may be related to the immune-modulating properties
of MTX.
Effects of S-adenosyl-L-methionine on platelet thromboxane
and vascular prostacyclin.
Author
De La Cruz JP; González-Correa JA; Martín-Aurioles E; Ortiz P; Sánchez de la Cuesta F
Address
Department of Pharmacology and Therapeutics, School of Medicine, University of Málaga,
Spain.
Source
Biochem Pharmacol, 1997 Jun 1, 53:11, 1761-3
Abstract
We therefore designed the present study to evaluate the effect of
S-adenosyl-L-methionine (SAMe) on the synthesis of platelet thromboxane and vascular
prostacyclin. The experimental materials were human blood and aortic rings from untreated
Wistar rats; and platelets and aortic rings from Wistar rats treated for 7 days with SAMe
at 5 or 10 mg/kg/day s.c. The administration of 10 mg/Kg/day of SAMe to rats significantly
increased vascular production of 6-keto-PGF1alpha. In vitro vascular production of
6-keto-PGF1alpha increased in a concentration-dependent manner when SAMe was incubated in
the range of 10(-7) to 10(-4) M. The greatest increase was 167 +/- 15%, obtained in
samples incubated with 5 x 10(-5) M SAMe. In aortic rings, lipid peroxidase production was
inhibited in a concentration-dependent manner in the SAMe range of 10(-7) to 10(-5) M.
Maximum inhibition (75.3 +/- 6.2%) was obtained with SAMe at 1.5 x 10(-5) M. Vascular
6-keto-PGF1alpha production showed a significant inverse linear correlation with vascular
lipid peroxide production (Y = -0.04x + 18.1, r = 0.7309, P < 0.0001).
Department of Rheumatology, Frederiksberg Hospital, Copenhagen, Denmark.
Source
Scand J Rheumatol, 1997, 26:3, 206-11
Abstract
The objective of this study was to test the efficacy of intravenously administered
S-adenosyl-L-methionine (SAMe) in patients with fibromyalgia (FM). Thirty-four
out-patients with fibromyalgia symptoms received SAMe 600 mg i.v. or placebo daily for 10
days in a cross-over trial. There was no significant difference in improvement in the
primary outcome: tender point change between the two treatment groups. There was a
tendency towards statistical significance in favour of SAMe on subjective perception of
pain at rest (p = 0.08), pain on movement (p = 0.11), and overall well-being (p = 0.17)
and slight improvement only on fatigue, quality of sleep, morning stiffness, and on the
Fibromyalgia Impact Questionnaire for pain. No effect could be observed on isokinetic
muscle strength, Zerrsen self-assessment questionnaire, and the face scale. No effect of
SAMe in patients with FM was found in this short term study.
Rapidity of onset of the antidepressant effect of parenteral S-adenosyl-L-methionine.
Author
Fava M; Giannelli A; Rapisarda V; Patralia A; Guaraldi GP
Address
Depression Research Program, Massachusetts General Hospital, Boston 02114, USA.
Source
Psychiatry Res, 1995 Apr 28, 56:3, 295-7
Abstract
A possible method of reducing the delay in antidepressant response is to use
S-adenosyl-L-methionine (SAMe), a naturally occurring compound that appears to have a
rapid onset of effect in the treatment of depression. In this open, multicenter study, 195
patients were given 400 mg of SAMe, administered parenterally, for 15 days. Depressive
symptoms remitted after both 7 and 15 days of treatment with SAMe, and no serious adverse
events were reported. Further studies with a double-blind design are needed to confirm
this preliminary indication that SAMe is a relatively safe and fast-acting antidepressant.
Department of Pharmacology, Mayo Medical School/Mayo Clinic/Mayo Foundation, Rochester,
MN 55905, USA.
Source
Pharmacogenetics, 1996 Feb, 6:1, 43-53
Abstract
Nicotinamide N-methyltransferase (NNMT) catalyses the N-methylation of nicotinamide and
other pyridines. Human liver NNMT activity shows large individual variations and a bimodal
frequency distribution, raising the possibility that this activity, like those of many
other methyltransferase enzymes, might be regulated by a genetic polymorphism. In an
attempt to develop an experimental animal model for pharmacogenetic studies of NNMT, we
determined optimal conditions for the measurement of hepatic NNMT activity in C57BL/6J
mice. Mouse liver NNMT was a cytoplasmic enzyme with a pH optimum of 7.4 and apparent Km
values for nicotinamide and S-adenosyl-L-methionine, cosubstrates for the reaction, of 370
and 6.5 microM, respectively. These properties were very similar to those of human liver
NNMT, as was the relative sensitivity of the mouse liver enzyme to a series of
methyltransferase inhibitors. Hepatic NNMT activity was then measured in tissue from male
mice of 10 inbred strains. Average levels of NNMT activity in these strains varied by up
to 14-fold and ranged from 1.13 +/- 0.18 U per mg protein (mean +/- SEM, n = 6) for
C3H/HeJ mice to 16.0 +/- 1.16 U per mg protein in C57BR/cdJ animals. Average hepatic NNMT
activities in female mice of six strains in which both sexes were studied varied from
five-fold higher than those in males for "low activity' strains, to not significantly
different for "high activity' strains. A series of properties of NNMT was then
compared in hepatic cytosol from male mice of three different strains - one with
"low' (C3H/HeJ), one with "intermediate' (DBA/2J), and one with "high'
(C57BL/6J) hepatic NNMT activity. There were no striking differences among these three
strains in hepatic NNMT pH optimum, substrate kinetics, IC50 values for inhibitors,
thermal stability or behavior during ion exchange chromatography. The existence of large
strain and gender-dependent variation in hepatic NNMT activity will make it possible to
use inbred mice for studies of the role of inheritance and gender in the regulation of
NNMT activity in this species, as well as for studies of the potential pharmacological and
toxicological consequences of variation in this important drug-metabolizing enzyme
activity.
Language of Publication
English
Unique Identifier
96252404
MeSH Heading (Major)
Liver|CY/*EN; Methyltransferases|AI/*GE/ME
MeSH Heading
Amodiaquine|ME; Animal; Calcium|ME; Chromatography, Ion Exchange; Enzyme Stability;
Female; Human; Hydrogen-Ion Concentration; Kinetics; Magnesium|ME; Male; Mice; Mice,
Inbred Strains; Niacinamide|ME; S-Adenosylhomocysteine|ME; S-Adenosylmethionine|ME; Sex
Characteristics; Support, Non-U.S. Gov't; Support, U.S. Gov't, P.H.S.; Time Factors
Recombinant human phenylethanolamine N-methyltransferase: overproduction in Escherichia
coli, purification, and characterization.
Author
Caine JM; Macreadie IG; Grunewald GL; McLeish MJ
Address
Victorian College of Pharmacy, Monash University, 381 Royal Parade, Parkville, Victoria,
3052, Australia.
Source
Protein Expr Purif, 1996 Sep, 8:2, 160-6
Abstract
The gene encoding phenylethanolamine N-methyltransferase (PNMT) has been amplified from
a human adrenal medulla cDNA library. Following ligation of the gene into a pET3a-derived
expression vector and transformation into Escherichia coli BL21(DE3)pLysS, PNMT was
expressed, yielding about 10% of the soluble protein. The enzyme was purified to
homogeneity by ammonium sulfate fractionation followed by ion-exchange chromatography and
gel filtration. The Km for phenylethanolamine and S-adenosyl-L-methionine were determined
to be 130 and 16 microM, respectively. The enzyme could be inhibited by reagents expected
to modify cysteine, arginine, tyrosine, and histidine residues, but not by methyl
acetimidate, a reagent expected to modify lysine residues.
Inhibition of human thiopurine methyltransferase by furosemide, bendroflumethiazide and
trichlormethiazide.
Author
Lysaa RA; Giverhaug T; Wold HL; Aarbakke J
Address
Department of Pharmacology, University of Troms, Norway.
Source
Eur J Clin Pharmacol, 1996, 49:5, 393-6
Abstract
RESULTS: Incubation in vitro of human recombinant and erythrocyte (RBC) thiopurine
methyl transferase (TPMT) with furosemide, bendroflumethiazide and trichlormethiazide
demonstrated inhibition of both enzyme preparations, with IC50 values of 170 microM, 360
microM and 1 mM, respectively. Kinetic studies revealed that the inhibition was mixed or
non-competitive with regard both to the thiopurine substrate 6-mercaptopurine (6-MP) and
the methyl donor S-adenosyl-L-methionine. CONCLUSION: Since S-methylation is a major
pathway in the metabolism of thiopurines, our data point to the possibility of a
clinically significant diuretic-thiopurine interaction in patients treated simultaneously
with these drugs.
Expression and purification of a human recombinant methyltransferase that repairs
damaged proteins.
Author
MacLaren DC; Clarke S
Address
Department of Chemistry and Biochemistry, University of California, Los Angeles
90095-1569, USA.
Source
Protein Expr Purif, 1995 Feb, 6:1, 99-108
Abstract
We report the construction of a plasmid (pDM2x) containing the coding sequence of the
more acidic isozyme II of the human protein-L-isoaspartate (D-aspartate)
O-methyltransferase (EC 2.1.1.77) and the overexpression and purification of the
recombinant protein. This intracellular enzyme is present in all tissues and can catalyze
the first step of a repair reaction where proteins containing abnormal L-isoaspartyl (or
D-aspartyl) residues can be converted to forms containing normal L-aspartyl residues. When
the methyl-transferase cDNA is expressed in Escherichia coli strain BL21 (DE3) under the
T7 phage promoter, we find that active enzyme is produced in amounts up to 20% of the
total soluble protein. We have developed a rapid and efficient purification method
utilizing a one column-step nonaffinity fractionation that allows for the preparation of
10.2 mg of homogeneous enzyme from 2.6 liters of Luria-Bertani broth culture in less than
24 h. The product is soluble and fully active (10,000 pmol of methyl groups transferred to
ovalbumin/mg enzyme/min from S-adenosyl-L-methionine at 37 degrees C). Conditions have
been developed to concentrate this enzyme to 30 mg/ml. Analyses of the purified enzyme by
N-terminal Edman sequencing and electrospray mass spectroscopy reveal that it is identical
to the human isozyme II with the exception that the N-terminal alanine residue is not
acetylated.
GSH transport in mitochondria: defense against TNF-induced oxidative stress and
alcohol-induced defect.
Author
Fernández-Checa JC; Kaplowitz N; García-Ruiz C; Colell A; Miranda M; Marí M; Ardite
E; Morales A
Address
Instituto de Investigaciones Biomédicas, Hospital Clinic i Provincial, Universidad de
Barcelona, Spain.
Source
Am J Physiol, 1997 Jul, 273:1 Pt 1, G7-17
Abstract
Mitochondria generate reactive oxygen species (ROS) as byproducts of molecular oxygen
consumption in the electron transport chain. Most cellular oxygen is consumed in the
cytochrome-c oxidase complex of the respiratory chain, which does not generate reactive
species. The ubiquinone pool of complex III of respiration is the major site within the
respiratory chain that generates superoxide anion as a result of a single electron
transfer to molecular oxygen. Superoxide anion and hydrogen peroxide, derived from the
former by superoxide dismutase, are precursor of hydroxyl radical through the
participation of transition metals. Glutathione (GSH) in mitochondria is the only defense
available to metabolize hydrogen peroxide. A small fraction of the total cellular GSH pool
is sequestered in mitochondria by the action of a carrier that transports GSH from the
cytosol to the mitochondrial matrix. Mitochondria are not only one of the main cellular
sources of ROS, they also are a key target of ROS. Mitochondria are subcellular targets of
cytokines, especially tumor necrosis factor (TNF); depletion of GSH in this organelle
renders the cell more susceptible to oxidative stress originating in mitochondria.
Ceramide generated during TNF signaling leads to increased production of ROS in
mitochondria. Chronic ethanol-fed hepatocytes are selectively depleted of GSH in
mitochondria due to a defective operation of the carrier responsible for transport of GSH
from the cytosol into the mitochondrial matrix. Under these conditions, limitation of the
mitochondrial GSH pool represents a critical contributory factor that sensitizes alcoholic
hepatocytes to the prooxidant effects of cytokines and prooxidants generated by oxidative
metabolism of ethanol. S-adenosyl-L-methionine prevents development of the ethanol-induced
defect. The mitochondrial GSH carrier has been functionally expressed in Xenopus laevis
oocytes microinjected with mRNA from rat liver. This critical carrier displays functional
characteristics distinct from other plasma membrane GSH carriers, such as its ATP
dependency, inhibitor specificity, and the size class of mRNA that encode the
corresponding carrier, suggesting that the mitochondrial carrier of GSH is a gene product
distinct from the plasma membrane transporters.
The mammalian immediate-early TIS21 protein and the leukemia-associated BTG1 protein
interact with a protein-arginine N-methyltransferase.
Author
Lin WJ; Gary JD; Yang MC; Clarke S; Herschman HR
Address
Molecular Biology Institute, Department of Chemistry and Biochemistry University of
California, Los Angeles, 90095, USA.
Source
J Biol Chem, 1996 Jun 21, 271:25, 15034-44
Abstract
The TIS21 immediate-early gene and leukemia-associated BTG1 gene encode proteins with
similar sequences. Two-hybrid analysis identified a protein that interacts with TIS21 and
BTG1. Sequence motifs associated with S-adenosyl-L-methionine binding suggested this
protein might have methyltransferase activity. A glutathione S-transferase (GST) fusion of
the putative methyltransferase modifies arginine residues, in appropriate protein
substrates, to form NG-monomethyl and NG,NG-dimethylarginine (asymmetric). We term the
protein- arginine N-methyltransferase (EC 2.1.1.23) gene "PRMT1, " for
protein-arginine methyltransferase 1. GST-TIS21 and GST-BTG1 fusion proteins qualitatively
and quantitatively modulate endogenous PRMT1 activity, using control and hypomethylated
RAT1 cell extracts as methyl-accepting substrates. PRMT1 message appears ubiquitous, and
is constitutive in mitogen-stimulated cells. Modulation of PRMT1 activity by transiently
expressed regulatory subunits may be an additional mode of signal transduction following
ligand stimulation.
Protein L-isoaspartyl methyltransferase from the nematode Caenorhabditis elegans:
genomic structure and substrate specificity.
Author
Kagan RM; Clarke S
Address
Department of Chemistry and Biochemistry, University of California, Los Angeles
90095-1569, USA.
Source
Biochemistry, 1995 Aug 29, 34:34, 10794-806
Abstract
We identified a protein L-isoaspartate (D-aspartate) O-methyltransferase (EC 2.1.1.77)
in the nematode worm Caenorhabditis elegans. The methylation of abnormal L-isoaspartyl
residues by this enzyme can lead to their conversion to L-aspartyl residues and represents
a protein repair step for polypeptides damaged by spontaneous reactions during the aging
process. We show that the levels of this enzyme increase 2-fold in C. elegans in the dauer
larval form, a developmental stage where the organism can survive for extended periods of
time. Utilizing degenerate oligonucleotide primers derived from conserved amino acid
sequences of mammalian, plant, and bacterial L-isoaspartyl methyltransferases and PCR
amplification, we made DNA probes that allowed us to obtain cDNA and genomic DNA clones
encoding this enzyme in the nematode. The deduced amino acid sequence is 53% identical to
the human enzyme and 29% identical to the Escherichia coli enzyme. Overexpression of the
cDNA for the C. elegans enzyme in E. coli gave an active product with micromolar Km values
for L-isoaspartyl-containing peptide substrates and for the methyl donor
S-adenosyl-L-methionine. No methylation of D-aspartyl-containing peptides was detected
under conditions where the human enzyme catalyzed this reaction, suggesting that the
ability to methylate D-aspartyl residues in addition to L-isoaspartyl residues was a later
evolutionary adaptation of this enzyme. The C. elegans gene for the methyltransferase,
designated pcm-1, was mapped to a single site in a 31 kb region in the central portion of
chromosome V. The gene is 3.2 kb in length and includes six introns. Although much
smaller, its genomic organization is similar to that of the corresponding mouse gene, with
identically positioned intron--exon splice junctions at five of seven sites. We propose
that this gene plays an important role in facilitating the long term survival of this
organisms.
Language of Publication
English
Unique Identifier
95391655; GENBANK/U09669; GENBANK/U15129
MeSH Heading (Major)
Caenorhabditis elegans|*EN; Genes, Helminth|*; Protein Methyltransferases|CH/*GE/*ME
WM Keck Structural Biology Laboratory, Cold Spring Harbor Laboratory, New York 11724,
USA.
Source
Curr Opin Struct Biol, 1995 Feb, 5:1, 4-10
Abstract
Enzymatic methylation of DNA plays important roles in both prokaryotes and eukaryotes.
Structural study of the HhaI DNA methyltransferase has provided considerable insight into
the chemistry of C5-cytosine methylation. The DNA-protein complex reveals a substrate
cytosine flipped out of the double helix during the reaction, and a novel two-loop
DNA-binding motif used for both sequence recognition and flipping the base. Structural
comparison of HhaI C5-cytosine methyltransferase, TaqI N6-adenine methyltransferase, and
catechol O-methyltransferase reveals a common catalytic domain structure, which might be
universal among S-adenosyl-L-methionine (SAM)-dependent methyltransferases.
Involvement of methionine in the synthesis of certain
membrane-associated nucleotide sugars by human amnion (WISH) cells.
Author
Wood RC
Address
Department of Microbiology and Immunology, University of Texas, Medical Branch,
Galveston, 77555-1019, USA.
Source
Cancer Lett, 1996 Feb 27, 100:1-2, 37-40
Abstract
A plasma membrane preparation from human amnion (WISH) cells contained uridine
diphosphate sugars and methyl-uridine diphosphate (mUDP) sugars. The synthesis of
mUDP-glucose, mUDP-mannose, and mUDP-fucose by the membrane preparation occurred when
supplemented with uridine-5'-diphosphate-glucose and S-adenosyl-L-methionine. It is
suggested that this newly recognized route for fucose biosynthesis might be employed by
certain transformed cells, and may partly account for the methionine
dependence of certain human tumors. Additionally, it is suggested that, in colon cancer, a
deficiency of folic acid and methionine might affect
mUDP-sugar biosynthesis rather than the methylation of DNA.
Pharmacokinetic profile of Mitoguazone (MGBG) in patients with AIDS related
non-Hodgkin's lymphoma.
Author
Rizzo J; Levine AM; Weiss GR; Pearce T; Kraynak M; Mueck R; Smith S; Von Hoff DD; Kuhn
JG
Address
Cancer Therapy and Research Center, San Antonio, TX, 78229, USA.
Source
Invest New Drugs, 1996, 14:2, 227-34
Abstract
Mitoguazone is a unique chemotherapeutic agent whose activity is believed to result
primarily from the competitive inhibition of S-adenosyl-methionine decarboxylase leading
to a disruption in polyamine biosynthesis. Initial clinical trials demonstrated that the
dose-limiting toxicities (mucositis and myelosuppression) of Mitoguazone were both dose
and schedule dependent. Early pharmacokinetic studies of Mitoguazone in man revealed a
prolonged half-life. Concurrent with a recent Phase II trial of Mitoguazone in patients
with AIDS related non-Hodgkin's lymphoma, the single dose pharmacokinetics of Mitoguazone
were characterized. Twelve patients received 600 mg/m2 of intravenous Mitoguazone over 30
minutes on an intermittent every 2 week schedule. Blood, urine, cerebrospinal fluid (CSF),
pleural fluid and tissue samples were collected and analyzed by HPLC. Mitoguazone was
cleared from the plasma triexponentially with a harmonic mean terminal half-life of 175
hours and a mean residence time of 192 hours. Peak plasma levels occurred immediately
post-infusion, ranged from 6.47 to 42.8 micrograms/ml, and remained (for an extended
period) well above the reported concentration for inhibition of polyamine biosynthesis.
Plasma clearance averaged 4.73 l/hr/m2 with a relatively large apparent volume of
distribution at steady-state of 1012 l/m2 indicating tissue sequestration. Renal excretion
of unchanged Mitoguazone accounted for an average of 15.8% of the dose within 48 to 72
hours post-administration. Detectable levels of drug were present in random voided samples
eight days post-dose. Mitoguazone levels in CSF ranged from 22 to 186 ng/ml post-dose with
CSF/plasma ratios ranging from 0.6% to 7%. The pleural fluid/plasma ratio was
approximately 1. Tissue levels of Mitoguazone were highest in the liver followed by lymph
node, spleen and the brain.
Treatment of nude mice with 4-amidinoindan -1- one2 '- amidinohydrazone, a new
S-adenosylmethionine decarboxylase inhibitor, delays growth and inhibits metastasis of
human melanoma cells.
Author
Gutman M; Beltran PJ; Fan D; Delworth MG; Singh RK; Wilson MR; Fidler IJ
Address
Department of Cell Biology, University of Texas M. D. Anderson Cancer Center, Houston
77030, USA.
Source
Melanoma Res, 1995 Jun, 5:3, 147-54
Abstract
CGP 48664A (4-amidinoindan-1-one2'-amidinohydrazone) is a novel inhibitor of
S-adenosyl-methionine decarboxylase (SAMDC), a key enzyme in the biosynthesis of
polyamines, which are themselves essential for proliferation of mammalian cells. Seven
different human melanoma cell lines were treated in vitro with CGP 48664A. High,
intermediate and low levels of cytostasis were induced in four, one and two melanoma
lines, respectively. This cytostasis was reversed by the addition of exogenous spermidine
or spermine to the culture medium. The heterogeneous low metastatic (CGP 48664A-resistant)
A375P cells and highly metastatic (CGP 48664A-sensitive) A375SM cells were implanted into
the subcutis or injected intravenously into nude mice. Systemic daily administration of
CGP 48664A significantly reduced the size of cutaneous lesions and the number of lung
metastases in mice implanted with A375SM cells. No beneficial effects were found in mice
injected with A375P cells. Drug activity was dose dependent, and maximal effects were
observed when treatment began in mice with small tumour burdens. The data suggest that CGP
48664A is effective against melanoma metastasis in nude mice and that its activity should
be tested in combination with other cytoreductive agents.
Activation-dependent carboxyl methylation of neutrophil G-protein gamma subunit.
Author
Philips MR; Staud R; Pillinger M; Feoktistov A; Volker C; Stock JB; Weissmann G
Address
Department of Medicine, New York University Medical Center, NY 10016.
Source
Proc Natl Acad Sci U S A, 1995 Mar 14, 92:6, 2283-7
Abstract
The gamma subunits of heterotrimeric guanine nucleotide-binding regulatory (G) proteins
(G gamma) are post-translationally processed at their C termini by prenylation,
proteolysis, and carboxyl methylation. Whereas prenylation of G gamma is required for
membrane association of G proteins, the role of carboxyl methylation is unknown. Here we
show that human neutrophils express G gamma 2 but not G gamma 3 or G gamma 7 and that
carboxyl methylation of G gamma 2 is associated with signal transduction. In a
reconstituted cell-free system, neutrophil G gamma 2 was labeled by the methyl donor
S-[methyl-3H]adenosyl-L-methionine. Carboxyl methylation was confirmed by alkaline
hydrolysis and quantitation of volatile [3H]methanol. Neutrophil G gamma 2 methylation was
stimulated by activation of G protein with guanosine 5'-[beta, gamma-thio]triphosphate. We
estimate that after 1 hr of G-protein activation at least 6% of the total pool of G gamma
2 was carboxyl-methylated. The inflammatory agonist fMet-Leu-Phe stimulated guanosine
5'-[beta,gamma-thio]triphosphate-dependent carboxyl methylation. Methylation of G gamma 2
was inhibited by the carboxyl methyltransferase inhibitor
N-acetyl-S-trans,trans-farnesylcysteine at concentrations that affected signal
transduction in neutrophils. These results demonstrate that activation of neutrophil Gi is
associated with alpha-carboxyl methyl esterification of G gamma 2 and suggest that
carboxyl methylation of G gamma may play a role in signal transduction.
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