The Oxidation of 5-Methyl- 14 C-tetrahydrofolate and Histidine-2- 14 C to 14 CO 2 in Vitamin B 12 -Deficient Rats 1

Abstract

Summary

When rats were fed a diet deficient in vitamin B₁₂ and limiting in methionine, the ¹⁴CO₂ production from L-histidine-2-¹⁴C was reduced in comparison with rats fed diets supplementd with vitamin B₁₂ and/or methionine. In contrast, the production of ¹⁴CO₂ from 5-¹⁴CH₃-tetrahydrofolic acid was not altered by vitamin B₁₂ deficiency or the level of dietary methionine. The T _max for the oxidation of 5-¹⁴CH₃-tetrahydrofolic acid to ¹⁴CO₂ was delayed in vitamin B₁₂ deficiency in comparison with normals, indicating that either an enzymatic reaction or transport into tissues becomes rate-limiting in the deficient state.