INTERMEDIARY METABOLISM OF DIPLOCOCCUS GLYCINOPHILUS I

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Abstract
Cell-free extracts catalyze the cleavage of glycine to one-carbon units in steps dependent on tetrahydrofolate, pyridoxal phosphate and diphosphopyridine nucleotide. Studies with glycine-1-C14 and glycine-2-Cl4 showed that CO2 is generated from the carboxyl carbon but not from the [alpha] -carbon when all three cofactors are added. The glycine-[alpha]-carbon is transferred to tetrahydrofolate, forming the hydroxymethyl derivative. An aldol condensation of the latter with a second glycine molecule gives rise to serine which is further deaminated to pyruvate. A reaction sequence is proposed for the generation of doubly labeled acetate from glycine-2-C14 by way of the above cleavage reactions and subsequent serine and pyruvate formation. A sequence is also proposed by which CO2 could be incorporated into both carbons of acetate by equilibriation with hydroxymethyl units and the [alpha]-carbon of glycine. A spectrophotometric assay for glycine cleavage is described.