Accepted name: 2-hydroxy-4-carboxymuconate semialdehyde hemiacetal dehydrogenase
Reaction: 4-carboxy-2-hydroxymuconate semialdehyde hemiacetal + NADP+ = 2-oxo-2H-pyran-4,6-dicarboxylate + NADPH + H+
Other name(s): 2-hydroxy-4-carboxymuconate 6-semialdehyde dehydrogenase; 4-carboxy-2-hydroxy-cis,cis-muconate-6-semialdehyde:NADP+ oxidoreductase; α-hydroxy-γ-carboxymuconic ε-semialdehyde dehydrogenase; 4-carboxy-2-hydroxymuconate-6-semialdehyde dehydrogenase; LigC; ProD
Systematic name: 4-carboxy-2-hydroxymuconate semialdehyde hemiacetal:NADP+ 2-oxidoreductase
Comments: The enzyme does not act on unsubstituted aliphatic or aromatic aldehydes or glucose; NAD+ can replace NADP+, but with lower affinity. The enzyme was initially believed to act on 4-carboxy-2-hydroxy-cis,cis-muconate 6-semialdehyde and produce 4-carboxy-2-hydroxy-cis,cis-muconate [1]. However, later studies showed that the substrate is the hemiacetal form [3], and the product is 2-oxo-2H-pyran-4,6-dicarboxylate [2,4].
1.  Maruyama, K., Ariga, N., Tsuda, M. and Deguchi, K. Purification and properties of α-hydroxy-γ-carboxymuconic ε-semialdehyde dehydrogenase. J. Biochem. (Tokyo) 83 (1978) 1125–1134. [PMID: 26671]
2.  Maruyama, K. Isolation and identification of the reaction product of α-hydroxy-γ-carboxymuconic ε-semialdehyde dehydrogenase. J. Biochem. 86 (1979) 1671–1677. [PMID: 528534]
3.  Maruyama, K. Purification and properties of 2-pyrone-4,6-dicarboxylate hydrolase. J. Biochem. (Tokyo) 93 (1983) 557–565. [PMID: 6841353]
4.  Masai, E., Momose, K., Hara, H., Nishikawa, S., Katayama, Y. and Fukuda, M. Genetic and biochemical characterization of 4-carboxy-2-hydroxymuconate-6-semialdehyde dehydrogenase and its role in the protocatechuate 4,5-cleavage pathway in Sphingomonas paucimobilis SYK-6. J. Bacteriol. 182 (2000) 6651–6658. [PMID: 11073908]
[EC created 1978 as EC, transferred 2011 to EC]
Transferred entry: 4-carboxy-2-hydroxymuconate-6-semialdehyde dehydrogenase. Now EC, 2-hydroxy-4-carboxymuconate semialdehyde hemiacetal dehydrogenase.
[EC created 1978, deleted 2011]
Accepted name: 2-hydroxymuconate-6-semialdehyde dehydrogenase
Reaction: 2-hydroxymuconate-6-semialdehyde + NAD+ + H2O = (2Z,4E)-2-hydroxyhexa-2,4-dienedioate + NADH + 2 H+
Glossary: 2-hydroxymuconate-6-semialdehyde = (2Z,4E)-2-hydroxy-6-oxohexa-2,4-dienoate
Other name(s): xylG (gene name); praB (gene name)
Systematic name: 2-hydroxymuconate-6-semialdehyde:NAD+ oxidoreductase
Comments: This substrate for this enzyme is formed by meta ring cleavage of catechol (EC, catechol 2,3-dioxygenase), and is an intermediate in the bacterial degradation of several aromatic compounds. Has lower activity with benzaldehyde [1]. Activity with NAD+ is more than 10-fold higher than with NADP+ [3]. cf. EC, aminomuconate-semialdehyde dehydrogenase.
1.  Inoue, J., Shaw, J.P., Rekik, M. and Harayama, S. Overlapping substrate specificities of benzaldehyde dehydrogenase (the xylC gene product) and 2-hydroxymuconic semialdehyde dehydrogenase (the xylG gene product) encoded by TOL plasmid pWW0 of Pseudomonas putida. J. Bacteriol. 177 (1995) 1196–1201. [PMID: 7868591]
2.  Orii, C., Takenaka, S., Murakami, S. and Aoki, K. Metabolism of 4-amino-3-hydroxybenzoic acid by Bordetella sp. strain 10d: A different modified meta-cleavage pathway for 2-aminophenols. Biosci. Biotechnol. Biochem. 70 (2006) 2653–2661. [PMID: 17090920]
3.  Kasai, D., Fujinami, T., Abe, T., Mase, K., Katayama, Y., Fukuda, M. and Masai, E. Uncovering the protocatechuate 2,3-cleavage pathway genes. J. Bacteriol. 191 (2009) 6758–6768. [PMID: 19717587]
[EC created 2012]
Accepted name: catechol 2,3-dioxygenase
Reaction: catechol + O2 = 2-hydroxymuconate-6-semialdehyde
Glossary: 2-hydroxymuconate-6-semialdehyde = (2Z,4E)-2-hydroxy-6-oxohexa-2,4-dienoate
Other name(s): 2,3-pyrocatechase; catechol 2,3-oxygenase; catechol oxygenase; metapyrocatechase; pyrocatechol 2,3-dioxygenase; xylE (gene name); catechol:oxygen 2,3-oxidoreductase (decyclizing)
Systematic name: catechol:oxygen 2,3-oxidoreductase (ring-opening)
Comments: Requires FeII. The enzyme initiates the meta-cleavage pathway of catechol degradation.
1.  Hayaishi, O. Direct oxygenation by O2, oxygenases. In: Boyer, P.D., Lardy, H. and Myrbäck, K. (Ed.), The Enzymes, 2nd edn, vol. 8, Academic Press, New York, 1963, pp. 353–371.
2.  Kojima, Y., Itada, N. and Hayaishi, O. Metapyrocatechase: a new catechol-cleaving enzyme. J. Biol. Chem. 236 (1961) 2223–2228. [PMID: 13757654]
3.  Nozaki, M., Kagamiyama, H. and Hayaishi, O. Metapyrocatechase. I. Purification, crystallization and some properties. Biochem. Z. 338 (1963) 582–590. [PMID: 14087325]
4.  Nakai, C., Hori, K., Kagamiyama, H., Nakazawa, T. and Nozaki, M. Purification, subunit structure, and partial amino acid sequence of metapyrocatechase. J. Biol. Chem. 258 (1983) 2916–2922. [PMID: 6826545]
5.  Junker, F., Field, J.A., Bangerter, F., Ramsteiner, K., Kohler, H.-P., Joannou, C.L., Mason, J.R., Leisinger, T. and Cook, A.M. Oxygenation and spontaneous deamination of 2-aminobenzenesulphonic acid in Alcaligenes sp. strain O-1 with subsequent meta ring cleavage and spontaneous desulphonation to 2-hydroxymuconic acid. Biochem. J. 300 (1994) 429–436. [PMID: 8002948]
6.  Junker, F., Leisinger, T. and Cook, A.M. 3-Sulphocatechol 2,3-dioxygenase and other dioxygenases (EC and EC 1.14.12.-) in the degradative pathways of 2-aminobenzenesulphonic, benzenesulphonic and 4-toluenesulphonic acids in Alcaligenes sp. strain O-1. Microbiology 140 (1994) 1713–1722. [PMID: 8075807]
[EC created 1965 as EC, transferred 1972 to EC, modified 1999, modified 2013]
Accepted name: 2-hydroxymuconate-6-semialdehyde hydrolase
Reaction: 2-hydroxymuconate-6-semialdehyde + H2O = formate + 2-oxopent-4-enoate
Glossary: 2-hydroxymuconate-6-semialdehyde = (2Z,4E)-2-hydroxy-6-oxohexa-2,4-dienoate
Other name(s): 2-hydroxy-6-oxohepta-2,4-dienoate hydrolase; 2-hydroxymuconic semialdehyde hydrolase; HMSH; HOD hydrolase; xylF (gene name); 2-hydroxymuconate-semialdehyde formylhydrolase; 2-hydroxymuconate-semialdehyde hydrolase
Systematic name: 2-hydroxymuconate-6-semialdehyde formylhydrolase
Comments: The enzyme is involved in the degradation of catechols.
1.  Sala-Trepat, J.M. and Evans, W.C. The meta cleavage of catechol by Azotobacter species. 4-Oxalocrotonate pathway. Eur. J. Biochem. 20 (1971) 400–413. [PMID: 4325686]
2.  Harayama, S., Rekik, M., Wasserfallen, A. and Bairoch, A. Evolutionary relationships between catabolic pathways for aromatics: conservtion of gene order and nucleotide sequences of catechol oxidation genes of pWW0 and NAH7 plasmids. MGG Mol. Gen. Genet. 210 (1987) 241–247. [PMID: 3481421]
3.  Diaz, E. and Timmis, K.N. Identification of functional residues in a 2-hydroxymuconic semialdehyde hydrolase. A new member of the α/β hydrolase-fold family of enzymes which cleaves carbon-carbon bonds. J. Biol. Chem. 270 (1995) 6403–6411. [PMID: 7890778]
[EC created 1990, modified 2013]