Decarboxylation of glycine by serine hydroxymethyl transferase ec in the presence of lipoic acid

Zieske, L.R.; Davis, L.

Journal of Biological Chemistry 258(17): 10355-10359


ISSN/ISBN: 0021-9258
Accession: 005093624

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Serine hydroxymethyltransferase [SHMT] and the glycine cleavage system are both present in [sheep, hog, beef] liver mitochondria and both bind glycine to form a pyridoxal 5'-phosphate carbanionic quinoid species. Lipoic acid had the ability to intercept the carbanionic intermediate formed from the binary complex of SHMT and glycine and form an intermediate adduct which is ultimately processed to yield CO2 and a methylamine adduct. Kinetic studies showed that the lipoic acid-dependent decarboxylation of glycine catalyzed by SHMT proceeds through a sequential mechanism. This lipoic acid-dependent decarboxylation catalyzed by SHMT is similar to the initial reaction of the glycine cleavage system and to the lipoic acid-dependent decarboxylation of glycine by the P-protein alone suggesting that both enzymes could serve in lieu of each other.