Influence of Vitamin Bi2 and Folacin on the Synthesis of Choline and Methionine by the Rat. ∗

Abstract

Summary

The role of vit. B₁₂ and folacin in the biosynthesis of choline and methionine has been studied and the following conclusions are warranted: 1. In the presence of adequate methyls (from choline), vit. Bi2 alone was as effective for methionine synthesis as when combined with folacin. When fed alone, folacin was ineffective. 2. In the presence of a limited supply of methyl groups, both folacin and vit. Bi2 were essential for the normal development of weanling rats. 3. Vit. Bi2 and folacin were essential for the synthesis of choline and of methionine from aminoethanol, homocystine, and a limited supply of betaine. 4. As a methyl donor for the synthesis of methionine from homocystine, betaine was at least as effective as choline, mole per mole. 5. Under the experimental conditions employed, the rate of synthesis of the methyl group or utilization of methanol for the methy-lation of homocystine to methionine and aminoethanol to choline was not fast enough to support normal development of weanling rats.