Cobalamin inactivation decreases purine and methionine synthesis in cultured lymphoblasts.
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چکیده
منابع مشابه
Cobalamin inactivation decreases purine and methionine synthesis in cultured lymphoblasts.
The megaloblastic anemia of cobalamin deficiency appears secondary to decreased methionine synthetase activity. Decreased activity of this enzyme should cause 5-methyltetrahydrofolate to accumulate intracellularly, and consequently, decrease purine and DNA synthesis; this is the basis of the "methylfolate trap" hypothesis of cobalamin deficiency. However, only some of the clinical and biochemic...
متن کاملCobalamin-dependent methionine synthase.
Cobalamin-dependent methionine synthase catalyzes the transfer of a methyl group from N5-methyltetrahydrofolate to homocysteine, producing tetrahydrofolate and methionine. Insufficient availability of cobalamin, or inhibition of methionine synthase by exposure to nitrous oxide, leads to diminished activity of this enzyme. In humans, severe inhibition of methionine synthase results in the develo...
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Deoxyadenosine (dAdo) and deoxyguanosine (dGuo) decrease methionine synthesis from homocysteine in cultured lymphoblasts; because of the possible trapping of 5-methyltetrahydrofolate this could lead to decreased purine nucleotide synthesis. Since purine deoxynucleosides could also inhibit purine synthesis de novo at an early step not involving folate metabolism, we measured in azaserine-treated...
متن کاملChronic Cobalamin Inactivation Impairs
It is suggested that these compounds have their effect in correcting folate polyglutamate synthesis by supplying formate for the formylation of tetrahydrofolate. Formyltetrahydrofolate, at least in the cobalamin-inactivated animal, is the required substrate for folate polyglutamate synthesis. Cobalamin is concerned with the maintenance of normal levels of methionine and this in turn is a major ...
متن کاملDe novo purine synthesis in cultured rat embryos undergoing organogenesis.
The cultured rat embryo undergoing organogenesis (9.5-11.5 days of gestation) together with its associated yolk sac synthesize purine nucleotides via the de novo synthetic pathway. Although both the embryo and its yolk sac contain significant levels of the purine base salvage enzymes adenine phosphoribosyltransferase and hypoxanthine phosphoribosyltransferase, the culture medium that consists l...
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ژورنال
عنوان ژورنال: Journal of Clinical Investigation
سال: 1985
ISSN: 0021-9738
DOI: 10.1172/jci111948