Influence of Vitamin B12 and Methionine on Levels of Folic Acid Compounds and Folate Enzymes in Rat Liver.

Abstract

The concentrations of folic acid coenzymes (determined by standard microbiological techniques) and the activities of 3 folate-dependent enzymes have been compared in the livers of rats kept on diets differing in vitamin B12 and methionine content. The basal diet contained: 20% soy assay protein (0. 3% methionine), 4% corn oil, 71% cerelose and sufficient salts and vitamins except B12. Supplements were 100 [mu]g/kg vitamin B12 and/or 1. 5% D, L-methionine. The level of methyltetrahydrofolate: homocysteine S-methyltransferase was found dependent on vitamin B12 and decreased by dietary methionine in much the same way as reported for chickens. Methylene-tetrahydro-folate reductase (E. C. 1. 1. 1. 68) and glutamate formiminotransferase (E. C. 2. 1. 2. 5. ) activities were not changed. The animals on the basal diet had very low levels of liver folates, especially conjugated forms, compared to animals supplemented with either vitamin B12 or methionine despite 5 mg/kg folic acid in the diet.