IUBMB Enzyme Nomenclature


Accepted name: phosphoserine transaminase

Reaction: (1) O-phospho-L-serine + 2-oxoglutarate = 3-phosphooxypyruvate + L-glutamate
(2) 4-phosphooxy-L-threonine + 2-oxoglutarate = (3R)-3-hydroxy-2-oxo-4-phosphooxybutanoate + L-glutamate

For diagram, click here or here or here for mechanism click here.

Other name(s): PSAT; phosphoserine aminotransferase; 3-phosphoserine aminotransferase; hydroxypyruvic phosphate-glutamic transaminase; L-phosphoserine aminotransferase; phosphohydroxypyruvate transaminase; phosphohydroxypyruvic-glutamic transaminase; phosphoserine aminotransferase; 3-O-phospho-L-serine:2-oxoglutarate aminotransferase; SerC; PdxC; 3PHP transaminase

Systematic name: O-phospho-L-serine:2-oxoglutarate aminotransferase

Comments: A pyridoxal-phosphate protein. This enzyme catalyses the second step in the phosphorylated pathway of serine biosynthesis in Escherichia coli [2,3]. It also catalyses the third step in the biosynthesis of the coenzyme pyridoxal 5'-phosphate in Escherichia coli (using Reaction 2 above) [3]. In Escherichia coli, pyridoxal 5'-phosphate is synthesized de novo by a pathway that involves EC (erythrose-4-phosphate dehydrogenase), EC (4-phosphoerythronate dehydrogenase), EC (phosphoserine transaminase), EC (4-hydroxythreonine-4-phosphate dehydrogenase), EC (pyridoxine 5'-phosphate synthase) and EC (with pyridoxine 5'-phosphate as substrate). Pyridoxal phosphate is the cofactor for both activities and therefore seems to be involved in its own biosynthesis [4]. Non-phosphorylated forms of serine and threonine are not substrates [4].

Links to other databases: BRENDA, EXPASY, GTD, KEGG, Metacyc, PDB, CAS registry number: 9030-90-4


1. Hirsch, H. and Greenberg, D.M. Studies on phosphoserine aminotransferase of sheep brain. J. Biol. Chem. 242 (1967) 2283-2287. [PMID: 6022873]

2. Pizer, L.I. The pathway and control of serine biosynthesis in Escherichia coli. J. Biol. Chem. 238 (1963) 3934-3944. [PMID: 14086727]

3. Zhao, G. and Winkler, M.E. A novel α-ketoglutarate reductase activity of the serA-encoded 3-phosphoglycerate dehydrogenase of Escherichia coli K-12 and its possible implications for human 2-hydroxyglutaric aciduria. J. Bacteriol. 178 (1996) 232-239. [PMID: 8550422]

4. Drewke, C., Klein, M., Clade, D., Arenz, A., Müller, R. and Leistner, E. 4-O-phosphoryl-L-threonine, a substrate of the pdxC(serC) gene product involved in vitamin B6 biosynthesis. FEBS Lett. 390 (1996) 179-182. [PMID: 8706854]

5. Zhao, G. and Winkler, M.E. 4-Phospho-hydroxy-L-threonine is an obligatory intermediate in pyridoxal 5'-phosphate coenzyme biosynthesis in Escherichia coli K-12. FEMS Microbiol. Lett. 135 (1996) 275-280. [PMID: 8595869]

[EC created 1972, modified 2006]

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