Role of Methylenetetrahydrofolic Acid Reductase in Regulation of Folic Acid Metabolism and its Relation to the Methyl Trap Hypothesis

Stokstad, E. L. R.; Chan, Mei-Lin; Watson, J. E.

doi:10.1515/9783111619453.241

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“…Methionine functions by way of the inhibitory effect of S-adenosylmethionine (AdoMet) on this enzyme (6) thereby similarly reducing 5-methyl-THF levels. Hypothyroidism has also been shown to increase 1 O-formyl-THF dehydrogenase (7,8) and methionine synthase (9,10).…”

Section: Introductionmentioning

confidence: 99%

Effect of Hormones and Protein Level on Induction of Enzymes Involved in Histidine Degradation and Folate Metabolism

Nair

Stokstad

1990

Pteridines

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SummaryThe effects of the hormones thyroxine, glucagon and hydrocortisone, and of protein level on hepatic histidase, urocanase, and certain folate enzymes were studied in rats. Hypothyroidism, induced either by feeding thiouracil or by thyroidectomy, increased histidase, urocanase, and the folate dependent enzyme formiminotransferase, and increased histidine metabolism as measured by oxidation of the 2-ring carbon of histidine to carbon dioxide. Hyperthyroidism, produced by feeding thyroid powder, decreased histidine oxidation and liver levels of this enzyme. Glucagon and hydrocortisone increased histidine oxidation and increased levels of histidase, urocanase and formiminotransferase . Elevated levels of casein and soy protein produced four to eight fold increases in histidase and urocanase, and 50% increases in formiminotransferase. Thus, increases in histidase and urocanase involved in the formation of formiminoglutamic acid (FIGlu) were accompanied by increases in the FIGlu metabolizing enzyme formiminotransferase.

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Section: Introductionmentioning

confidence: 99%