Oxidation/Reduction Reactions can be catalyzed by oxidoreductase that involves the transfer of electrons from one molecule, the reductant, also called the electron donor, to another, the oxidant, also called the electron acceptor. Oxidoreductase usually utilizes NADP or NAD+ as cofactors.12
The substrate oxidized is regarded as a hydrogen or electron donor. The classification is based on ‘donor:acceptor oxidoreductase’. The common name is ‘dehydrogenase’, wherever this is possible; as an alternative, ‘acceptor reductase’ can be used. ‘Oxidase’ is used only where O2 is an acceptor. Classification is difficult in some cases, because of the lack of specificity towards the acceptor.
Oxidoreductases can be either oxidases or dehydrogenases. Oxidases are generally involved when molecular oxygen functions as an acceptor of hydrogen or electrons. However, dehydrogenases work by oxidizing a substrate through transferring hydrogen to an acceptor that is either NAD/NADP or a flavin enzyme. Peroxidases, hydroxylases, oxygenases, and reductases also belong to oxidoreductases. Peroxidases are placed in peroxisomes, and could catalyze the reduction of hydrogen peroxide. Hydroxylases give hydroxyl groups to its substrates. Oxygenases could incorporate oxygen from molecular oxygen into organic substrates. In most cases, reductases can act like oxidases, but catalyzing reductions.
Oxidoreductases are sorted as EC 1 in the EC number classification of enzymes and can be further classified into 22 subclasses.
The catalyzed reactions are similar to the following reaction:
Ared + Box → Aox + Bred
where A is the reductant (electron donor) and B is the oxidant (electron acceptor).
In biochemical reactions, the redox reactions are sometimes more difficult to observe, such as this reaction from glycolysis:
Pi + glyceraldehyde-3-phosphate + NAD+ → NADH + H+ + 1,3-bisphosphoglycerate
where NAD+ is the oxidant (electron acceptor), and glyceraldehyde-3-phosphate functions as reductant ( electron donor).
For a detailed information on class, subclass or sub-subclass of oxidoreductases, please visit ExplorEnz.
| Family Number | Characterized | Pfam |
|---|---|---|
| OR1 | B1XDG0 | ADH_zinc_N; ADH_N_2 |
| OR2 | Q52028 | Rieske; Ring_hydroxyl_A |
| OR3 | A0A0U1WKA6; E1CIA4; F7V1S0; H3JUE4; M9NZ71; V9P074 | Oxidored_FMN; Pyr_redox_2 |
| OR4 | E7FL40; F7V1S3; H3JUE2; M9P0B3 | FAD_binding_2 |
| OR5 | E7FL41; F7V1S2; H3JUE3; M9NYU8 | adh_short_C2 |
| OR6 | Q2EYY8 | HpaB; HpaB_N |
| OR7 | Q74HL7; Q74HL8 | FMN_red |
| OR8 | P42106; A2VA43 | Cupin_2 |
| OR9 | G2IMF2; Q2G4H9 | NAD_binding_10 |
OR1: OR1_1 / OR1_2 / OR1_3 / OR1_4 / OR1_5 / OR1_6 / OR1_7 / OR1_8 / OR1_9
OR2: No subfamily
OR3: No subfamily
OR4: OR4_1 / OR4_2 / OR4_3 / OR4_4 / OR4_5 / OR4_6 / OR4_7 / OR4_8
OR5: OR5_1 / OR5_2 / OR5_3 / OR5_4 / OR5_5 / OR5_6 / OR5_7 / OR5_8 / OR5_9
OR6: OR6_1 OR6_2 OR6_3 OR6_4 OR6_5 OR6_6 OR6_7 OR6_8 OR6_9
OR7: No subfamily
OR8: OR8_1 / OR8_2 / OR8_3 / OR8_4 / OR8_5 / OR8_6 / OR8_7 / OR8_8 / OR8_9 / OR8_10 / OR8_11 / OR8_12 / OR8_13 / OR8_14 / OR8_15 / OR8_16 /OR8_17 / OR8_18 / OR8_19 / OR8_20 / OR8_21 / OR8_22 / OR8_23 / OR8_24 / OR8_25 / OR8_26
OR9: OR9_1 / OR9_2 / OR9_3 / OR9_4 / OR9_5 / OR9_6 / OR9_7 / OR9_8 / OR9_9
OR1 1.3.1.48 ; 1.3.1.74 ; 1.3.1.n3
OR2 1.14.12.19 ; 1.14.12.12 ; 1.14.12.18 ; 1.14.12.3 ; 1.14.12.11 ; 1.14.12.24
OR3 1.3.1.115 ; 1.3.1.116 ; 1.3.1.34
OR4 1.1.5.3 ; 1.4.3.16 ; 1.3.5.1 ; 1.3.5.4 ; 1.3.99.33 ; 1.3.1.6 ; 1.3.4.1
OR5 1.1.1.1 ; 1.1.1.330 ; 1.1.1.100 ; 1.3.1.9 ; 1.1.1.62 ; 1.1.1.300 ; 1.3.1.87 ; 1.5.1.3 ; 1.5.1.50 ; 1.1.1.105 ; 1.1.1.30 ; 1.1.1.53 ; 1.3.1.34 ; 1.1.1.239 ; 1.1.1.304 ; 1.1.1.184 ; 1.1.1.209 ; 1.1.1.10 ; 1.1.1.47 ; 1.1.1.146 ; 1.1.1.381 ; 1.1.1.36 ; 1.1.1.n12 ; 4.2.1.119 ; 2.3.1.41 ; 1.1.1.141 ; 1.1.1.35 ; 1.1.1.51 ; 1.1.1.138 ; 1.1.1.298 ; 1.1.1.315 ; 1.3.1.56 ; 1.1.1.178 ; 1.3.1.38 ; 1.1.1.127 ; 1.1.1.270 ; 1.1.1.236 ; 1.1.1.64 ; 1.1.1.313 ; 1.1.1.250 ; 1.3.1.29 ; 1.1.1.16 ; 1.1.1.385 ; 1.3.1.28 ; 4.2.1.107 ; 1.1.1.395 ; 1.1.1.69 ; 1.1.1.289 ; 1.1.1.276 ; 1.3.1.39 ; 1.1.1.159 ; 1.3.1.25 ; 1.3.1.60 ; 1.1.1.391 ; 1.1.1.331 ; 1.1.1.252 ; 1.1.1.163 ; 1.1.1.206 ; 1.3.1.58 ; 1.1.1.326 ; 1.1.1.76 ; 1.1.1.390 ; 1.1.1.288 ; 1.1.1.295 ; 1.3.1.49 ; 1.1.1.6 ; 1.1.1.216 ; 1.1.1.119 ; 1.1.1.n4 ; 1.1.1.401 ; 1.1.1.413 ; 1.1.1.162 ; 1.2.1.62 ; 1.3.1.19 ; 1.1.1.403 ; 1.1.1.268 ; 1.1.1.393 ; 1.1.1.269 ; 1.1.1.223 ; 1.1.1.243 ; 1.1.1.386 ; 1.1.1.175 ; 1.1.1.140 ; 1.1.1.362 ; 1.1.1.377 ; 1.1.1.311 ; 1.1.1.392 ; 1.1.1.233 ; 1.1.1.107 ; 1.1.1.14 ; 1.1.1.173 ; 2.3.1.94 ; 1.3.1.104
OR6 1.14.14.9 ; 1.14.13.29
OR7 1.7.1.17 ; 1.6.5.2 ; 1.3.99.33 ; 1.5.1.36 ; 1.6.5.6
OR8 2.7.7.13 ; 1.13.11.54 ; 5.3.1.8 ; 1.15.1.1 ; 1.13.11.24
OR9 5.1.3.2 ; 1.1.1.219 ; 1.1.1.234 ; 1.23.1.1 ; 1.23.1.2 ; 1.23.1.3 ; 5.1.3.5 ; 1.23.1.4 ; 1.3.1.45 ; 1.1.1.319 ; 1.1.1.318
Eric J. Toone (2006). Advances in Enzymology and Related Areas of Molecular Biology, Protein Evolution (Volume 75 ed.). Wiley-Interscience. ISBN 0471205036. ↩
Nicholas C. Price; Lewis Stevens (1999). Fundamentals of Enzymology: The Cell and Molecular Biology of Catalytic Proteins (Third ed.). USA: Oxford University Press. ISBN 019850229X. ↩