Accepted name: pyruvate dehydrogenase (NADP+)
Reaction: pyruvate + CoA + NADP+ = acetyl-CoA + CO2 + NADPH
Glossary: methyl viologen = 1,1′-dimethyl-4,4′-bipyridine-1,1′-diium
Systematic name: pyruvate:NADP+ 2-oxidoreductase (CoA-acetylating)
Comments: The Euglena enzyme can also use FAD or methyl viologen as acceptor, more slowly. The enzyme is inhibited by oxygen.
1.  Inui, H., Miyatake, K., Nakano, Y. and Kitaoka, S. Occurrence of oxygen-sensitive, NADP +-dependent pyruvate dehydrogenase in mitochondria of Euglena gracilis. J. Biochem. (Tokyo) 96 (1984) 931–934. [PMID: 6438078]
2.  Inui, H., Ono, K., Miyatake, K., Nakano, Y. and Kitaoka, S. Purification and characterization of pyruvate:NADP+ oxidoreductase in Euglena gracilis. J. Biol. Chem. 262 (1987) 9130–9135. [PMID: 3110154]
[EC created 1989]
Accepted name: aldehyde ferredoxin oxidoreductase
Reaction: an aldehyde + H2O + 2 oxidized ferredoxin = a carboxylate + 2 H+ + 2 reduced ferredoxin
Other name(s): AOR
Systematic name: aldehyde:ferredoxin oxidoreductase
Comments: This is an oxygen-sensitive enzyme that contains tungsten-molybdopterin and iron-sulfur clusters. Catalyses the oxidation of aldehydes (including crotonaldehyde, acetaldehyde, formaldehyde and glyceraldehyde) to their corresponding acids. However, it does not oxidize glyceraldehyde 3-phosphate [see EC, glyceraldehyde-3-phosphate dehydrogenase (ferredoxin)]. Can use ferredoxin or methyl viologen but not NAD(P)+ as electron acceptor.
1.  Mukund, S. and Adams, M.W.W. The novel tungsten-iron-sulfur protein of the hyperthermophilic archaebacterium, Pyrococcus furiosus, is an aldehyde ferredoxin oxidoreductase - evidence for its participation in a unique glycolytic pathway. J. Biol. Chem. 266 (1991) 14208–14216. [PMID: 1907273]
2.  Johnson, J.L., Rajagopalan, K.V., Mukund, S. and Adams, M.W.W. Identification of molybdopterin as the organic-component of the tungsten cofactor in four enzymes from hyperthermophilic archaea. J. Biol. Chem. 268 (1993) 4848–4852. [PMID: 8444863]
3.  Chan, M.K., Mukund, S., Kletzin, A., Adams, M.W.W. and Rees, D.C. Structure of a hyperthermophilic tungstopterin enzyme, aldehyde ferredoxin oxidoreductase. Science 267 (1995) 1463–1469. [PMID: 7878465]
4.  Roy, R., Menon, A.L. and Adams, M.W.W. Aldehyde oxidoreductases from Pyrococcus furiosus. Methods Enzymol. 331 (2001) 132–144. [PMID: 11265456]
[EC created 2003]
Transferred entry: carbon-monoxide dehydrogenase (acceptor). Now EC, carbon-monoxide dehydrogenase (ferredoxin)
[EC created 1982, modified 1990, modified 2003, deleted 2016]
Accepted name: carboxylate reductase
Reaction: an aldehyde + acceptor + H2O = a carboxylate + reduced acceptor
Other name(s): aldehyde:(acceptor) oxidoreductase
Systematic name: aldehyde:acceptor oxidoreductase
Comments: A tungsten protein. Methyl viologen can act as acceptor. In the reverse direction, non-activated acids are reduced by reduced viologens to aldehydes, but not to the corresponding alcohols.
1.  White, H., Strobl, G., Feicht, R. and Simon, H. Carboxylic acid reductase: a new tungsten enzyme catalyses the reduction of non-activated carboxylic acids to aldehydes. Eur. J. Biochem. 184 (1989) 89–96. [PMID: 2550230]
[EC created 1992]
Transferred entry: benzoyl-CoA reductase. Now EC
[EC created 1999, deleted 2011]
Accepted name: urocanate reductase
Reaction: dihydrourocanate + acceptor = urocanate + reduced acceptor
Glossary: urocanate = 3-(1H-imidazol-4-yl)prop-2-enoate
dihydrourocanate = 3-(1H-imidazol-4-yl)propanoate
Other name(s): urdA (gene name)
Systematic name: dihydrourocanate:acceptor oxidoreductase
Comments: The enzyme from the bacterium Shewanella oneidensis MR-1 contains a noncovalently-bound FAD and a covalently-bound FMN. It functions as part of an anaerobic electron transfer chain that utilizes urocanate as the terminal electron acceptor. The activity has been demonstrated with the artificial donor reduced methyl viologen.
1.  Bogachev, A.V., Bertsova, Y.V., Bloch, D.A. and Verkhovsky, M.I. Urocanate reductase: identification of a novel anaerobic respiratory pathway in Shewanella oneidensis MR-1. Mol. Microbiol. 86 (2012) 1452–1463. [PMID: 23078170]
[EC created 2013]
Accepted name: nitrite reductase (NO-forming)
Reaction: nitric oxide + H2O + ferricytochrome c = nitrite + ferrocytochrome c + 2 H+
Glossary: nitric oxide = NO = nitrogen(II) oxide
Other name(s): cd-cytochrome nitrite reductase; [nitrite reductase (cytochrome)] [misleading, see comments.]; cytochrome c-551:O2, NO2+ oxidoreductase; cytochrome cd; cytochrome cd1; hydroxylamine (acceptor) reductase; methyl viologen-nitrite reductase; nitrite reductase (cytochrome; NO-forming)
Systematic name: nitric-oxide:ferricytochrome-c oxidoreductase
Comments: The reaction is catalysed by two types of enzymes, found in the perimplasm of denitrifying bacteria. One type comprises proteins containing multiple copper centres, the other a heme protein, cytochrome cd1. Acceptors include c-type cytochromes such as cytochrome c-550 or cytochrome c-551 from Paracoccus denitrificans or Pseudomonas aeruginosa, and small blue copper proteins such as azurin and pseudoazurin. Cytochrome cd1 also has oxidase and hydroxylamine reductase activities. May also catalyse the reaction of hydroxylamine reductase (EC since this is a well-known activity of cytochrome cd1.
1.  Miyata, M. and Mori, T. Studies on denitrification. X. The "denitrifying enzyme" as a nitrite reductase and the electron donating system for denitrification. J. Biochem. (Tokyo) 66 (1969) 463–471. [PMID: 5354021]
2.  Chung, C.W. and Najjar, V.A. Cofactor requirements for enzymatic denitrification. I. Nitrite reductase. J. Biol. Chem. 218 (1956) 617–625. [PMID: 13295215]
3.  Walker, G.C. and Nicholas, D.J.D. Nitrite reductase from Pseudomonas aeruginosa. Biochim. Biophys. Acta 49 (1961) 350–360. [PMID: 13782716]
4.  Singh, J. Cytochrome oxidase from Pseudomonas aeruginosa. III. Reduction of hydroxylamine. Biochim. Biophys. Acta 333 (1974) 28–36. [PMID: 19396990]
5.  Michalski, W.P. and Nicholas, D.J.D. Molecular characterization of a copper-containing nitrite reductase from Rhodopseudomonas sphaeriodes forma sp. Denitrificans. Biochim. Biophys. Acta 828 (1985) 130–137.
6.  Godden, J.W., Turley, S., Teller, D.C., Adman, E.T., Liu, M.Y., Payne, W.J. and Legall, J. The 2.3 angstrom X-ray structure of nitrite reductase from Achromobacter cycloclastes. Science 253 (1991) 438–442. [PMID: 1862344]
7.  Williams, P.A., Fulop, V., Leung, Y.C., Chan, C., Moir, J.W.B., Howlett, G., Ferguson, S.J., Radford, S.E. and Hajdu, J. Pseudospecific docking surfaces on electron transfer proteins as illustrated by pseudoazurin, cytochrome c-550 and cytochrome cd1 nitrite reductase. Nat. Struct. Biol. 2 (1995) 975–982. [PMID: 7583671]
8.  Hole, U.H., Vollack, K.U., Zumft, W.G., Eisenmann, E., Siddiqui, R.A., Friedrich, B. and Kroneck, P.M.H. Characterization of the membranous denitrification enzymes nitrite reductase (cytochrome cd1) and copper-containing nitrous oxide reductase from Thiobacillus denitrificans. Arch. Microbiol. 165 (1996) 55–61. [PMID: 8639023]
9.  Zumft, W.G. Cell biology and molecular basis of denitrification. Microbiol. Mol. Biol. Rev. 61 (1997) 533–616. [PMID: 9409151]
10.  Ferguson, S.J. Nitrogen cycle enzymology. Curr. Opin. Chem. Biol. 2 (1998) 182–193. [PMID: 9667932]
11.  Vijgenboom, E., Busch, J.E. and Canters, G.W. In vitro studies disprove the obligatory role of azurin in denitrification in Pseudomonas aeruginosa and show that azu expression is under the control of RpoS and ANR. Microbiology 143 (1997) 2853–2863. [PMID: 9308169]
[EC created 1961, modified 1976, modified 2001, modified 2002 (EC created 1961 as EC, transferred 1964 to EC, modified 1976, incorporated 2002, EC created 1965, incorporated 2002)]
Deleted entry: sulfite reductase. Now covered by EC, assimilatory sulfite reductase (NADPH) and EC, assimilatory sulfite reductase (ferredoxin).
[EC created 1972, deleted 2015]
Accepted name: adenylyl-sulfate reductase
Reaction: AMP + sulfite + acceptor = adenylyl sulfate + reduced acceptor
Other name(s): adenosine phosphosulfate reductase; adenosine 5′-phosphosulfate reductase; APS-reductase; APS reductase; AMP, sulfite:(acceptor) oxidoreductase (adenosine-5′-phosphosulfate-forming)
Systematic name: AMP,sulfite:acceptor oxidoreductase (adenosine-5′-phosphosulfate-forming)
Comments: An iron flavoprotein (FAD). Methyl viologen can act as acceptor.
1.  Michaels, G.B., Davidson, J.T. and Peck, H.D., Jr. A flavin-sulfite adduct as an intermediate in the reaction catalyzed by adenylyl sulfate reductase from Desulfovibrio vulgaris. Biochem. Biophys. Res. Commun. 39 (1970) 321–328. [PMID: 5421934]
[EC created 1972]
Accepted name: hydrogen:quinone oxidoreductase
Reaction: H2 + menaquinone = menaquinol
Glossary: methyl viologen = 1,1′-dimethyl-4,4′-bipyridine-1,1′-diium
benzyl viologen = 1,1′-dibenzyl-4,4′-bipyridine-1,1′-diium
Other name(s): hydrogen-ubiquinone oxidoreductase; hydrogen:menaquinone oxidoreductase; membrane-bound hydrogenase; quinone-reactive Ni/Fe-hydrogenase
Systematic name: hydrogen:quinone oxidoreductase
Comments: Contains nickel, iron-sulfur clusters and cytochrome b. Also catalyses the reduction of water-soluble quinones (e.g. 2,3-dimethylnaphthoquinone) or viologen dyes (benzyl viologen or methyl viologen).
1.  Dross, F., Geisler, V., Lenger, R., Theis, F., Krafft, T., Fahrenholz, F., Kojro, E. , Duchêne, A., Tripier, D., Juvenal, K. and Kröger, A. The quinone-reactive Ni/Fe-hydrogenase of Wolinella succinogenes. Eur. J. Biochem. 206 (1992) 93–102. [PMID: 1587288]
2.  Dross, F., Geisler, V., Lenger, R., Theis, F., Krafft, T., Fahrenholz, F., Kojro, E., Duchene, A., Tripier, D. and Juvenal, K. Erratum to "The quinone-reactive Ni/Fe-hydrogenase of Wolinella succinogenes". Eur. J. Biochem. 214 (1993) 949–950. [PMID: 8319698]
3.  Gross, R., Simon, J., Lancaster, C.R.D. and Kroger, A. Identification of histidine residues in Wolinella succinogenes hydrogenase that are essential for menaquinone reduction by H-2. Mol. Microbiol. 30 (1998) 639–646. [PMID: 9822828]
4.  Bernhard, M., Benelli, B., Hochkoeppler, A., Zannoni, D. and Friedrich, B. Functional and structural role of the cytochrome b subunit of the membrane-bound hydrogenase complex of Alcaligenes eutrophus H16. Eur. J. Biochem. 248 (1997) 179–186. [PMID: 9310376]
5.  Ferber, D.M. and Maier, R.J. Hydrogen-ubiquinone oxidoreductase activity by the Bradyrhizobium japonicum membrane-bound hydrogenase. FEMS Microbiol. Lett. 110 (1993) 257–264. [PMID: 8354459]
6.  Ishii, M., Omori, T., Igarashi, Y., Adachi, O., Ameyama, M. and Kodama, T. Methionaquinone is a direct natural electron-acceptor for the membrane-bound hydrogenase in Hydrogenobacter thermophilus strain TK-6. Agric. Biol. Chem. 55 (1991) 3011–3016.
[EC created 1999 as EC, transferred 2002 to EC]
Accepted name: coenzyme F420 hydrogenase
Reaction: H2 + oxidized coenzyme F420 = reduced coenzyme F420
Glossary: coenzyme F420 = N-(N-{O-[5-(8-hydroxy-2,4-dioxo-2,3,4,10-tetrahydropyrimido[4,5-b]quinolin-10-yl)-5-deoxy-L-ribityl-1-phospho]-(S)-lactyl}-γ-L-glutamyl)-L-glutamate
Other name(s): 8-hydroxy-5-deazaflavin-reducing hydrogenase; F420-reducing hydrogenase; coenzyme F420-dependent hydrogenase
Systematic name: hydrogen:coenzyme F420 oxidoreductase
Comments: An iron-sulfur flavoprotein (FAD) containing nickel. The enzyme from some sources contains selenocysteine. The enzyme also reduces the riboflavin analogue of F420, flavins and methyl viologen, but to a lesser extent. The hydrogen acceptor coenzyme F420 is a deazaflavin derivative.
1.  Adams, M.W.W., Mortenson, L.E. and Chen, J.-S. Hydrogenase. Biochim. Biophys. Acta 594 (1981) 105–176. [PMID: 6786341]
2.  Yamazaki, S. A selenium-containing hydrogenase from Methanococcus vannielii. Identification of the selenium moiety as a selenocysteine residue. J. Biol. Chem. 257 (1982) 7926–7929. [PMID: 6211447]
3.  Fox, J.A., Livingston, D.J., Orme-Johnson, W.H. and Walsh, C.T. 8-Hydroxy-5-deazaflavin-reducing hydrogenase from Methanobacterium thermoautotrophicum: 1. Purification and characterization. Biochemistry 26 (1987) 4219–4228. [PMID: 3663585]
4.  Muth, E., Morschel, E. and Klein, A. Purification and characterization of an 8-hydroxy-5-deazaflavin-reducing hydrogenase from the archaebacterium Methanococcus voltae. Eur. J. Biochem. 169 (1987) 571–577. [PMID: 3121317]
5.  Baron, S.F. and Ferry, J.G. Purification and properties of the membrane-associated coenzyme F420-reducing hydrogenase from Methanobacterium formicicum. J. Bacteriol. 171 (1989) 3846–3853. [PMID: 2738024]
[EC created 1989 as EC, transferred 2002 to EC]
Accepted name: tetrachloroethene reductive dehalogenase
Reaction: trichloroethene + chloride + acceptor = tetrachloroethene + reduced acceptor
Glossary: methyl viologen = 1,1′-dimethyl-4,4′-bipyridine-1,1′-diium
Other name(s): tetrachloroethene reductase
Systematic name: acceptor:trichloroethene oxidoreductase (chlorinating)
Comments: This enzyme allows the common pollutant tetrachloroethene to support bacterial growth and is responsible for disposal of a number of chlorinated hydrocarbons. The reaction occurs in the reverse direction. The enzyme also reduces trichloroethene to dichloroethene. Although the physiological reductant is unknown, the supply of reductant in some organisms involves menaquinol, which is reduced by molecular hydrogen via the action of EC, hydrogen:quinone oxidoreductase. The enzyme contains a corrinoid and two iron-sulfur clusters. Methyl viologen can act as electron donor in vitro.
1.  Holliger, C, Wohlfarth, G. and Diekert, G. Reductive dechlorination in the energy metabolism of anaerobic bacteria. FEMS Microbiol. Rev. 22 (1998) 383–398.
2.  Glod, G., Angst, W., Holliger, C. and Schwarzenbach, R.P. Corrinoid-mediated reduction of tetrachloroethene, trichloroethene, and trichlorofluoroethene in homogeneous aqueous solution: Reaction kinetics and reaction mechanisms. Environ. Sci. Technol. 31 (1997) 253–260.
3.  Neumann, A., Wohlfarth, G. and Diekert, G. Purification and characterization of tetrachloroethene reductive dehalogenase from Dehalospirillum multivorans. J. Biol. Chem. 271 (1996) 16515–16519. [PMID: 8663199]
4.  Schumacher, W., Holliger, C., Zehnder, A.J.B. and Hagen, W.R. Redox chemistry of cobalamin and iron-sulfur cofactors in the tetrachloroethene reductase of Dehalobacter restrictus. FEBS Lett. 409 (1997) 421–425. [PMID: 9224702]
5.  Schumacher, W. and Holliger, C. The proton/electron ratio of the menaquinone-dependent electron transport from dihydrogen to tetrachloroethene in "Dehalobacter restrictus". J. Bacteriol. 178 (1996) 2328–2333. [PMID: 8636034]
[EC created 2001 as EC, transferred 2017 to EC]
Transferred entry: tetrachloroethene reductive dehalogenase. Now EC, tetrachloroethene reductive dehalogenase
[EC created 2001, deleted 2017]