The Enzyme Database

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Accepted name: L-threonine 3-dehydrogenase
Reaction: L-threonine + NAD+ = L-2-amino-3-oxobutanoate + NADH + H+
Other name(s): L-threonine dehydrogenase; threonine 3-dehydrogenase; threonine dehydrogenase; TDH
Systematic name: L-threonine:NAD+ oxidoreductase
Comments: This enzyme acts in concert with EC, glycine C-acetyltransferase, in the degradation of threonine to glycine. This threonine-degradation pathway is common to prokaryotic and eukaryotic cells and the two enzymes involved form a complex [2]. In aqueous solution, the product L-2-amino-3-oxobutanoate can spontaneously decarboxylate to form aminoacetone.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9067-99-6
1.  Green, M.L. and Elliott, W.H. The enzymic formation of aminoacetone from threonine and its further metabolism. Biochem. J. 92 (1964) 537–549. [PMID: 4284408]
2.  Hartshorne, D. and Greenberg, D.M. Studies on liver threonine dehydrogenase. Arch. Biochem. Biophys. 105 (1964) 173–178. [DOI] [PMID: 14165492]
3.  Newman, E.B., Kapoor, V. and Potter, R. Role of L-threonine dehydrogenase in the catabolism of threonine and synthesis of glycine by Escherichia coli. J. Bacteriol. 126 (1976) 1245–1249. [PMID: 7548]
4.  Epperly, B.R. and Dekker, E.E. L-Threonine dehydrogenase from Escherichia coli. Identification of an active site cysteine residue and metal ion studies. J. Biol. Chem. 266 (1991) 6086–6092. [PMID: 2007567]
[EC created 1972]
Accepted name: 3-hydroxy acid dehydrogenase
Reaction: L-allo-threonine + NADP+ = aminoacetone + CO2 + NADPH + H+ (overall reaction)
(1a) L-allo-threonine + NADP+ = L-2-amino-3-oxobutanoate + NADPH + H+
(1b) L-2-amino-3-oxobutanoate = aminoacetone + CO2 (spontaneous)
Glossary: L-allo-threonine = (2S,3S)-2-amino-3-hydroxybutanoic acid
aminoacetone = 1-aminopropan-2-one
L-2-amino-3-oxobutanoate = (2S)-2-amino-3-oxobutanoate
Other name(s): ydfG (gene name); YMR226c (gene name)
Systematic name: L-allo-threonine:NADP+ 3-oxidoreductase
Comments: The enzyme, purified from the bacterium Escherichia coli and the yeast Saccharomyces cerevisiae, shows activity with a range of 3- and 4-carbon 3-hydroxy acids. The highest activity is seen with L-allo-threonine and D-threonine. The enzyme from Escherichia coli also shows high activity with L-serine, D-serine, (S)-3-hydroxy-2-methylpropanoate and (R)-3-hydroxy-2-methylpropanoate. The enzyme has no activity with NAD+ or L-threonine (cf. EC, L-threonine 3-dehydrogenase).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
1.  Fujisawa, H., Nagata, S. and Misono, H. Characterization of short-chain dehydrogenase/reductase homologues of Escherichia coli (YdfG) and Saccharomyces cerevisiae (YMR226C). Biochim. Biophys. Acta 1645 (2003) 89–94. [DOI] [PMID: 12535615]
[EC created 2014, modified 2015]
Accepted name: glycine C-acetyltransferase
Reaction: acetyl-CoA + glycine = CoA + L-2-amino-3-oxobutanoate
Other name(s): 2-amino-3-ketobutyrate CoA ligase; 2-amino-3-ketobutyrate coenzyme A ligase; 2-amino-3-ketobutyrate-CoA ligase; glycine acetyltransferase; aminoacetone synthase; aminoacetone synthetase; KBL; AKB ligase
Systematic name: acetyl-CoA:glycine C-acetyltransferase
Comments: This is a pyridoxal-phosphate-dependent enzyme that acts in concert with EC, L-threonine 3-dehydrogenase, in the degradation of threonine to form glycine [3]. This threonine degradation pathway is common to prokaryotic and eukaryotic cells and the two enzymes involved form a complex [4].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 37257-11-7
1.  McGilvray, D. and Morris, J.G. Utilization of L-threonine by a species of Arthrobacter. A novel catabolic role for "aminoacetone synthase". Biochem. J. 112 (1969) 657–671. [PMID: 5821726]
2.  Mukherjee, J.J. and Dekker, E.E. Purification, properties, and N-terminal amino acid sequence of homogeneous Escherichia coli 2-amino-3-ketobutyrate CoA ligase, a pyridoxal phosphate-dependent enzyme. J. Biol. Chem. 262 (1987) 14441–14447. [PMID: 3117785]
3.  Edgar, A.J. and Polak, J.M. Molecular cloning of the human and murine 2-amino-3-ketobutyrate coenzyme A ligase cDNAs. Eur. J. Biochem. 267 (2000) 1805–1812. [DOI] [PMID: 10712613]
4.  Schmidt, A., Sivaraman, J., Li, Y., Larocque, R., Barbosa, J.A., Smith, C., Matte, A., Schrag, J.D. and Cygler, M. Three-dimensional structure of 2-amino-3-ketobutyrate CoA ligase from Escherichia coli complexed with a PLP-substrate intermediate: inferred reaction mechanism. Biochemistry 40 (2001) 5151–5160. [DOI] [PMID: 11318637]
[EC created 1972]

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