Publications

• A novel alpha-ketoglutarate reductase activity of the serA-encoded 3-phosphoglycerate dehydrogenase of Escherichia coli K-12 and its possible implications for human 2-hydroxyglutaric aciduria.

  Zhao G., Winkler M.E.

  Escherichia coli serA-encoded 3-phosphoglycerate (3PG) dehydrogenase catalyzes the first step of the major phosphorylated pathway of L-serine (Ser) biosynthesis. The SerA enzyme is evolutionarily related to the pdxB gene product, 4-phosphoerythronate dehydrogenase, which catalyzes the second step ... >> More

  Escherichia coli serA-encoded 3-phosphoglycerate (3PG) dehydrogenase catalyzes the first step of the major phosphorylated pathway of L-serine (Ser) biosynthesis. The SerA enzyme is evolutionarily related to the pdxB gene product, 4-phosphoerythronate dehydrogenase, which catalyzes the second step in one branch of pyridoxal 5'-phosphate coenzyme biosynthesis. Both the Ser and pyridoxal 5'-phosphate biosynthetic pathways use the serC(pdxF)-encoded transaminase in their next steps. In an analysis of these parallel pathways, we attempted to couple the transaminase and dehydrogenase reactions in the reverse direction. Unexpectedly, we found that the SerA enzyme catalyzes a previously undetected reduction of alpha-ketoglutarate (alpha KG) to 2-hydroxyglutaric acid (HGA). Numerous criteria ruled out the possibility that this SerA alpha KG reductase activity was caused by contamination in the substrate or purified enzyme preparations. HGA was confirmed as the product of the SerA alpha KG reductase reaction by thin-layer chromatography and by enzyme assays showing that both the D- and L-isomers of HGA were substrates for the reverse (dehydrogenase) reaction. Detailed steady-state kinetic analyses showed that alpha KG reduction (apparent Michaelis-Menten constant [Km(app)] = 88 microM; apparent catalytic constant [kcat(app)] = 33.3 s-1) and 3-phosphohydroxypyruvate reduction (Km(app) = 3.2 microM; kcatapp = 27.8 s-1), which is the reverse reaction of 3PG oxidation, were the major in vitro activities of the SerA enzyme. The SerA alpha KG reductase was inhibited by Ser, D-HGA, 3PG, and glycine (Gly), whereas the D-HGA dehydrogenase was inhibited by Ser, alpha KG, 3-phosphohydroxypyruvate, and Gly. The implications of these findings for the regulation of Ser biosynthesis, the recycling of NADH, and the enzymology of 2-hydroxyacid dehydrogenases are discussed. Since the same pathway of Ser biosynthesis seems to be present in all organisms, these results suggest that a mutation in the human SerA homolog may contribute to the neurometabolic diseases D- and L-2-hydroxyglutaric aciduria, which lead to the accumulation of D-HGA and L-HGA, respectively. << Less

  J. Bacteriol. 178:232-239(1996) [PubMed] [EuropePMC]

  This publication is cited by 3 other entries.

• THE PATHWAY AND CONTROL OF SERINE BIOSYNTHESIS IN ESCHERICHIA COLI.

  PIZER L.I.

  J Biol Chem 238:3934-3944(1963) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• 4-O-phosphoryl-L-threonine, a substrate of the pdxC(serC) gene product involved in vitamin B6 biosynthesis.

  Drewke C., Klein M., Clade D., Arenz A., Mueller R., Leistner E.

  The Escherichia coli pdxC(serC) gene codes for a transaminase (EC 2.6.1.52). The gene is involved in both pyridoxine (vitamin B6) and serine biosynthesis and was overexpressed as a MalE/PdxC(SerC) fusion protein. The fusion protein was purified by affinity chromatography on an amylose resin and hy ... >> More

  The Escherichia coli pdxC(serC) gene codes for a transaminase (EC 2.6.1.52). The gene is involved in both pyridoxine (vitamin B6) and serine biosynthesis and was overexpressed as a MalE/PdxC(SerC) fusion protein. The fusion protein was purified by affinity chromatography on an amylose resin and hydrolyzed in the presence of protease factor Xa. Both the fusion protein and the PdxC(SerC) protein were characterized (K(M) value, turnover number, optimum pH). Both enzymes used 4-O-phosphoryl-L-threonine rather than 4-hydroxy-L-threonine as a substrate indicating that the phosphorylated rather than the non-phosphorylated amino acid is involved in pyridoxine biosynthesis. Pyridoxal phosphate was shown to be the cofactor for both enzymes and therefore seems to be involved in its own biosynthesis. << Less

  FEBS Lett. 390:179-182(1996) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Studies on phosphoserine aminotransferase of sheep brain.

  Hirsch H., Greenberg D.M.

  J Biol Chem 242:2283-2287(1967) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• 4-phospho-hydroxy-L-threonine is an obligatory intermediate in pyridoxal 5'-phosphate coenzyme biosynthesis in Escherichia coli K-12.

  Zhao G., Winkler M.E.

  We show that thrB-encoded homoserine kinase is required for growth of Escherichia coli K-12 pdxB mutants on minimal glucose medium supplemented with 4-hydroxy-L-threonine (synonym, 3-hydroxyhomoserine) or D-glycolaldehyde. This result is consistent with a model in which 4-phospho-hydroxy-L-threoni ... >> More

  We show that thrB-encoded homoserine kinase is required for growth of Escherichia coli K-12 pdxB mutants on minimal glucose medium supplemented with 4-hydroxy-L-threonine (synonym, 3-hydroxyhomoserine) or D-glycolaldehyde. This result is consistent with a model in which 4-phospho-hydroxy-L-threonine (synonym, 3-hydroxyhomoserine phosphate), rather than 4-hydroxy-L-threonine, is an obligatory intermediate in pyridoxal 5'-phosphate biosynthesis. Ring closure using 4-phospho-hydroxy-L-threonine as a substrate would lead to formation of pyridoxine 5'-phosphate, and not pyridoxine, as the first B6-vitamer synthesized de novo. These considerations suggest that E. coli pyridoxal/pyridoxamine/pyridoxine kinase is not required for the main de novo pathway of pyridoxal 5'-phosphate biosynthesis, and instead plays a role only in the B6-vitamer salvage pathway. << Less

  FEMS Microbiol. Lett. 135:275-280(1996) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.