In vivo oxidation of the methyl group of hepatic 5-methyltetrahydrofolate

Abstract

Methionine given parenterally to rats caused rapid disappearance of methyltetra-hydrofolate from the liver and a corresponding rise in tetrahydrofolate and formyl-tetrahydrofolate concentrations. When [ 14C]H3-H4folate was given, methionine caused an increased [14C]O2 excretion, indicating that oxidation of the methyl group had occurred. Methionine was more effective than Sadenosylmethionine at causing oxidation, but serine was ineffective. The lowest dose ofmethionine to produce an effect was 0·5 μmol, which is less than the daily dietary intake in a rat. The data suggest that the concentration ofmethylfolate in rat livers is controlled by the concentrations of methionine.