Glycine Metabolism

Abstract

Abstract One of the four proteins involved in the cleavage of glycine to 1-carbon units and the transfer of electrons from glycine to diphosphopyridine nucleotide is a flavoprotein. Precipitation of the protein with acid ammonium sulfate in the presence of 1 m potassium bromide separated the coenzyme from the apoenzyme. The latter was fully reactivated by incubation with flavin adenine dinucleotide, but showed no activity with flavin mononucleotide. The flavoprotein could be reduced either by glycine or by reduced diphosphopyridine nucleotide. When reduced by the latter, no protein other than the flavoprotein was required for the electron transfer, but to achieve a measurable rate of reduction by glycine it was necessary to add the three other proteins plus tetrahydrofolate. Dihydrofolate was entirely inactive in the system.