EC	1.1.1.381
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 1.1.1.103, L-threonine 3-dehydrogenase).
References:	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. [PMID: 12535615]
[EC 1.1.1.381 created 2014, modified 2015]
EC	4.1.2.5
Accepted name:	L-threonine aldolase
Reaction:	L-threonine = glycine + acetaldehyde
Other name(s):	L-threonine acetaldehyde-lyase
Systematic name:	L-threonine acetaldehyde-lyase (glycine-forming)
Comments:	A pyridoxal-phosphate protein. This enzyme is specific for L-threonine and can not utilize L-allo-threonine. Different from EC 4.1.2.49, L-allo-threonine aldolase, and EC 4.1.2.48, low-specificity L-threonine aldolase.
References:	1.  Dainty, R.H. Purification and properties of threonine aldolase from Clostridium pasteurianum. Biochem. J. 117 (1970) 585–592. [PMID: 5419751] 2.  Karasek, M.A. and Greenberg, D.M. Studies on the properties of threonine aldolases. J. Biol. Chem. 227 (1957) 191–205. [PMID: 13449064]
[EC 4.1.2.5 created 1961, deleted 1972, reinstated 1976, modified 2011]
EC	4.1.2.48
Accepted name:	low-specificity L-threonine aldolase
Reaction:	(1) L-threonine = glycine + acetaldehyde (2) L-allo-threonine = glycine + acetaldehyde
Other name(s):	LtaE
Systematic name:	L-threonine/L-allo-threonine acetaldehyde-lyase (glycine-forming)
Comments:	Requires pyridoxal phosphate. The low-specificity L-threonine aldolase can act on both L-threonine and L-allo-threonine [1,2]. The enzyme from Escherichia coli can also act on L-threo-phenylserine and L-erythro-phenylserine [4]. The enzyme can also catalyse the aldol condensation of glycolaldehyde and glycine to form 4-hydroxy-L-threonine, an intermediate of pyridoxal phosphate biosynthesis [3]. Different from EC 4.1.2.5, L-threonine aldolase, and EC 4.1.2.49, L-allo-threonine aldolase.
References:	1.  Yamada, H., Kumagai, H., Nagate, T. and Yoshida, H. Crystalline threonine aldolase from Candida humicola. Biochem. Biophys. Res. Commun. 39 (1970) 53–58. [PMID: 5438301] 2.  Kumagai, H., Nagate, T., Yoshida, H. and Yamada, H. Threonine aldolase from Candida humicola. II. Purification, crystallization and properties. Biochim. Biophys. Acta 258 (1972) 779–790. [PMID: 5017702] 3.  Liu, J.Q., Nagata, S., Dairi, T., Misono, H., Shimizu, S. and Yamada, H. The GLY1 gene of Saccharomyces cerevisiae encodes a low-specific L-threonine aldolase that catalyzes cleavage of L-allo-threonine and L-threonine to glycine—expression of the gene in Escherichia coli and purification and characterization of the enzyme. Eur. J. Biochem. 245 (1997) 289–293. [PMID: 9151955] 4.  Liu, J.Q., Dairi, T., Itoh, N., Kataoka, M., Shimizu, S. and Yamada, H. Gene cloning, biochemical characterization and physiological role of a thermostable low-specificity L-threonine aldolase from Escherichia coli. Eur. J. Biochem. 255 (1998) 220–226. [PMID: 9692922] 5.  Kim, J., Kershner, J.P., Novikov, Y., Shoemaker, R.K. and Copley, S.D. Three serendipitous pathways in E. coli can bypass a block in pyridoxal-5′-phosphate synthesis. Mol. Syst. Biol. 6:436 (2010). [PMID: 21119630]
[EC 4.1.2.48 created 2011]
EC	4.1.2.49
Accepted name:	L-allo-threonine aldolase
Reaction:	L-allo-threonine = glycine + acetaldehyde
Systematic name:	L-allo-threonine acetaldehyde-lyase (glycine-forming)
Comments:	Requires pyridoxal phosphate. This enzyme, characterized from the bacterium Aeromonas jandaei, is specific for L-allo-threonine and can not act on either L-threonine or L-serine. Different from EC 4.1.2.5, L-threonine aldolase, and EC 4.1.2.48, low-specificity L-threonine aldolase. A previously listed enzyme with this name, EC 4.1.2.6, was deleted in 1971 after it was found to be identical to EC 2.1.2.1, glycine hydroxymethyltransferase.
References:	1.  Kataoka, M., Wada, M., Nishi, K., Yamada, H. and Shimizu, S. Purification and characterization of L-allo-threonine aldolase from Aeromonas jandaei DK-39. FEMS Microbiol. Lett. 151 (1997) 245–248. [PMID: 9228760]
[EC 4.1.2.49 created 2011]