Accepted name: 4-hydroxymuconic-semialdehyde dehydrogenase
Reaction: 4-hydroxymuconic semialdehyde + NAD+ + H2O = maleylacetate + NADH + 2 H+
Systematic name: 4-hydroxymuconic-semialdehyde:NAD+ oxidoreductase
Comments: Involved in the 4-nitrophenol degradation pathway.
1.  Spain, J.C. and Gibson, D.T. Pathway for bioremediation of p-nitrophenol in a Moraxella sp. Appl. Environ. Microbiol. 57 (1991) 812–819. [PMID: 16348446]
[EC created 2000]
Accepted name: maleylacetate reductase
Reaction: 3-oxoadipate + NAD(P)+ = 2-maleylacetate + NAD(P)H + H+
Other name(s): maleolylacetate reductase
Systematic name: 3-oxoadipate:NAD(P)+ oxidoreductase
1.  Gaal, A.B. and Neujahr, H.Y. Maleylacetate reductase from Trichosporon cutaneum. Biochem. J. 185 (1980) 783–786. [PMID: 7387635]
2.  Gaal, A.B. and Neujahr, H.Y. Induction of phenol-metabolizing enzymes in Trichosporon cutaneum. Arch. Microbiol. 130 (1981) 54–58. [PMID: 7305599]
[EC created 1983]
Accepted name: 2-hydroxy-1,4-benzoquinone reductase
Reaction: 2-hydroxy-1,4-benzoquinone + NADH + H+ = hydroxyquinol + NAD+
Glossary: hydroxyquinol = 1,2,4-trihydroxybenzene
Other name(s): hydroxybenzoquinone reductase; 1,2,4-trihydroxybenzene:NAD oxidoreductase
Systematic name: NADH:2-hydroxy-1,4-benzoquinone oxidoreductase
Comments: A flavoprotein (FMN) that differs in substrate specificity from other quinone reductases. The enzyme in Burkholderia cepacia is inducible by 2,4,5-trichlorophenoxyacetate.
1.  Zaborina, O., Daubaras, D.L., Zago, A., Xun, L., Saido, K. , Klem,T., Nikolic, D. and Chakrabarty, A.M. Novel pathway for conversion of chlorohydroxyquinol to maleylacetate in Burkholderia cepacia AC1100. J. Bacteriol. 180 (1998) 4667–4675. [PMID: 9721310]
[EC created 2000, modified 2004]
Accepted name: hydroxyquinol 1,2-dioxygenase
Reaction: hydroxyquinol + O2 = maleylacetate
Glossary: hydroxyquinol = 1,2,4-trihydroxybenzene
maleylacetate = (2Z)-4-oxohex-2-enedioate
Other name(s): hydroxyquinol dioxygenase; benzene-1,2,4-triol:oxygen 1,2-oxidoreductase (decyclizing); benzene-1,2,4-triol:oxygen 1,2-oxidoreductase (ring-opening)
Systematic name: hydroxyquinol:oxygen 1,2-oxidoreductase (ring-opening)
Comments: An iron protein. Highly specific; catechol and pyrogallol are acted on at less than 1% of the rate at which hydroxyquinol is oxidized.
1.  Sze, I.S.-Y. and Dagley, S. Properties of salicylate hydroxylase and hydroxyquinol 1,2-dioxygenase purified from Trichosporon cutaneum. J. Bacteriol. 159 (1984) 353–359. [PMID: 6539772]
2.  Ferraroni, M., Seifert, J., Travkin, V.M., Thiel, M., Kaschabek, S., Scozzafava, A., Golovleva, L., Schlomann, M. and Briganti, F. Crystal structure of the hydroxyquinol 1,2-dioxygenase from Nocardioides simplex 3E, a key enzyme involved in polychlorinated aromatics biodegradation. J. Biol. Chem. 280 (2005) 21144–21154. [PMID: 15772073]
3.  Hatta, T., Nakano, O., Imai, N., Takizawa, N. and Kiyohara, H. Cloning and sequence analysis of hydroxyquinol 1,2-dioxygenase gene in 2,4,6-trichlorophenol-degrading Ralstonia pickettii DTP0602 and characterization of its product. J. Biosci. Bioeng. 87 (1999) 267–272. [PMID: 16232466]
[EC created 1989, modified 2013]
Accepted name: carboxymethylenebutenolidase
Reaction: 4-carboxymethylenebut-2-en-4-olide + H2O = 4-oxohex-2-enedioate
Other name(s): maleylacetate enol-lactonase; dienelactone hydrolase; carboxymethylene butenolide hydrolase
Systematic name: 4-carboxymethylenebut-2-en-4-olide lactonohydrolase
1.  Schmidt, E. and Knackmuss, H.-J. Chemical structure and biodegradability of halogenated aromatic compounds. Conversion of chlorinated muconic acids into maleoylacetic acid. Biochem. J. 192 (1980) 339–347. [PMID: 7305906]
[EC created 1983]
Accepted name: 4-sulfomuconolactone hydrolase
Reaction: 4-sulfomuconolactone + H2O = maleylacetate + sulfite
Glossary: 4-sulfomuconolactone = 4-carboxymethylen-4-sulfobut-2-en-olide = 2-(5-oxo-2-sulfo-2,5-dihydrofuran-2-yl)acetic acid
maleylacetate = (2Z)-4-oxohex-2-enedioate
Systematic name: 4-sulfomuconolactone sulfohydrolase
Comments: The enzyme was isolated from the bacteria Hydrogenophaga intermedia and Agrobacterium radiobacter S2. It catalyses a step in the degradation of 4-sulfocatechol.
1.  Halak, S., Basta, T., Burger, S., Contzen, M., Wray, V., Pieper, D.H. and Stolz, A. 4-sulfomuconolactone hydrolases from Hydrogenophaga intermedia S1 and Agrobacterium radiobacter S2. J. Bacteriol. 189 (2007) 6998–7006. [PMID: 17660282]
[EC created 2012]

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