Methylation of Homocystine by Chicks Deficient in Vitamin B 12 . ∗

Abstract

Conclusions

Chicks very deficient in vit B₁₂ grew as well when homocystine and betaine were added to a methionine-deficient diet as when a comparable amount of methionine was added. No evidence was obtained that vit B₁₂ increased the efficiency with which preformed methyl groups were tranferred to homocystine since the effects of vit B₁₂ were additive to those of methionine or its equivalents of homocystine plus labile methyl. It appears likely, however, that when the chick's diet lacks methyl groups vit B₁₂ is concerned in the synthesis of such groups and their combination with homocystine to form methionine. Formation of methionine by this procedure, however, is limited and insufficient to meet the needs of the chick.