Vitamin B12 and the Synthesis of Thymine and Choline in the Chick

Abstract

The presence of large amounts of methionine in the diet of the chick did not dilute out the uptake of formate-¹⁴C into liver choline and it was concluded that chicks do not transfer methyl groups from methionine to choline. The uptake of formate-¹⁴C into thymine in the chick bursa and into choline in the chick liver was dependent upon the presence of adequate dietary supplements of both methionine and vitamin B₁₂. The data suggest that some step in de novo methyl synthesis or the transfer of one-carbon units to choline and thymine, or both, require a cobamide for a role separate from its role in methionine synthesis.