In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule (the reductant, also called the hydrogen acceptor or electron donor) to another (the oxidant, also called the hydrogen donor or electron acceptor). For example, an enzyme that catalyzed this reaction would be an oxidoreductase:
- A– + B → A + B–
Additional recommended knowledge
In this example, A is the reductant (electron donor) and B is the oxidant (electron acceptor).
In biochemical reactions, the redox reactions are sometimes more difficult to see, such as this reaction from glycolysis:
- Pi + glyceraldehyde-3-phosphate + NAD+ → NADH + H+ + 1,3-bisphosphoglycerate
In this reaction, NAD+ is the oxidant (electron acceptor), and glyceraldehyde-3-phosphate is the reductant (electron donor).
Nomenclature
Proper names of oxidoreductases are formed as "donor:acceptor oxidoreductase." However, other names are much more common. The common name is "donor dehydrogenase" when possible, such as glyceraldehyde-3-phosphate dehydrogenase for the second reaction above. Common names are also sometimes formed as "acceptor reductase", such as NAD+ reductase. "Donor oxidase" is a special case where O2 is the acceptor.
Classification
Oxidoreductases are classified as EC 1 in the EC number classification of enzymes. Oxidoreductases can be further classified into 22 subclasses:
- EC 1.1 includes oxidoreductases that act on the CH-OH group of donors (alcohol oxidoreductases)
- EC 1.2 includes oxidoreductases that act on the aldehyde or oxo group of donors
- EC 1.3 includes oxidoreductases that act on the CH-CH group of donors (CH-CH oxidoreductases)
- EC 1.4 includes oxidoreductases that act on the CH-NH2 group of donors (Amino acid oxidoreductases, Monoamine oxidase)
- EC 1.5 includes oxidoreductases that act on CH-NH group of donors
- EC 1.6 includes oxidoreductases that act on NADH or NADPH
- EC 1.7 includes oxidoreductases that act on other nitrogenous compounds as donors
- EC 1.8 includes oxidoreductases that act on a sulfur group of donors
- EC 1.9 includes oxidoreductases that act on a heme group of donors
- EC 1.10 includes oxidoreductases that act on diphenols and related substances as donors
- EC 1.11 includes oxidoreductases that act on peroxide as an acceptor (peroxidases)
- EC 1.12 includes oxidoreductases that act on hydrogen as donors
- EC 1.13 includes oxidoreductases that act on single donors with incorporation of molecular oxygen (oxygenases)
- EC 1.14 includes oxidoreductases that act on paired donors with incorporation of molecular oxygen
- EC 1.15 includes oxidoreductases that act on superoxide radicals as acceptors
- EC 1.16 includes oxidoreductases that oxidize metal ions
- EC 1.17 includes oxidoreductases that act on CH or CH2 groups
- EC 1.18 includes oxidoreductases that act on iron-sulfur proteins as donors
- includes oxidoreductases that act on reduced flavodoxin as a donor
- includes oxidoreductases that act on phosphorus or arsenic in donors
- EC 1.21 includes oxidoreductases that act on X-H and Y-H to form an X-Y bond
- EC 1.97 includes other oxidoreductases
See also
| Oxidoreductases: alcohol oxidoreductases (EC 1.1) |
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| 1.1.1 NAD/NADP acceptor | Carbohydrate dehydrogenases - Alcohol dehydrogenase - Glycerol-3-phosphate dehydrogenase - L-xylulose reductase - Aldose reductase - Lactate dehydrogenase - 3-Hydroxyacyl CoA dehydrogenase - Malate dehydrogenase - Isocitrate dehydrogenase - Phosphogluconate dehydrogenase - Glucose-6-phosphate dehydrogenase - HMG-CoA reductase - Β-Ketoacyl ACP reductase - Hydroxysteroid dehydrogenase: 11 Beta (HSD11B1, HSD11B2) - 3 Beta (3-beta-HSD) - 17 Beta - Carnitine dehydrogenase - Beta-hydroxybutyryl-CoA dehydrogenase - IMP dehydrogenase - DXP reductoisomerase |
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| 1.1.3 oxygen acceptor | Glucose oxidase - L-gulonolactone oxidase - Xanthine oxidase |
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| Oxidoreductases: CH-CH oxidoreductases (EC 1.3) |
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| 1.3.1. NAD/NADP acceptor | Enoyl-acyl carrier protein reductase/Enoyl ACP reductase - 7-Dehydrocholesterol reductase - Biliverdin reductase - 2,4 Dienoyl-CoA reductase |
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| 1.3.3. Oxygen acceptor | Dihydroorotate dehydrogenase - Coproporphyrinogen III oxidase - Protoporphyrinogen oxidase - |
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| 1.3.5. Quinone | Succinate - coenzyme Q reductase |
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| 1.3.99. Other acceptors | Fumarate reductase - Butyryl CoA dehydrogenase - Acyl CoA dehydrogenase - 5-alpha reductase - Glutaryl-CoA dehydrogenase - Isovaleryl coenzyme A dehydrogenase |
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| CH-NH2 oxidoreductases (EC 1.4) - primarily amino acid oxidoreductases |
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| 1.4.1 - NAD/NADP acceptor | Glutamate dehydrogenase (GLUD1) |
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| 1.4.3 - oxygen acceptor | D-amino acid oxidase - Amine oxidase - Lysyl oxidase - Monoamine oxidase |
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| 1.4.4 - disulfide acceptor | Glycine decarboxylase complex |
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| 1.4.99 - other acceptors | D-amino acid dehydrogenase - Amine dehydrogenase |
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| CH-NH oxidoreductases (EC 1.5) |
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| 1.5.1 - NAD or NADP acceptor | Dihydrofolate reductase - Saccharopine dehydrogenase - Methylenetetrahydrofolate reductase |
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| 1.5.3 - oxygen acceptor | Dihydrobenzophenanthridine oxidase - Sarcosine oxidase |
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| 1.5.5 - quinone acceptor | Electron-transferring-flavoprotein dehydrogenase |
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| NADH or NADPH oxidoreductases (EC 1.6) |
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| Methemoglobin reductase - NADPH oxidase (P91-PHOX) - NADH dehydrogenase |
| Oxidoreductases: sulfur oxidoreductases (EC 1.8) |
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| Dihydrolipoamide dehydrogenase - Glutathione reductase - Thioredoxin reductase - Sulfite oxidase |
| Oxidoreductases: monooxygenases (EC 1.13) |
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| 1.13.11 - two atoms of oxygen | Catechol dioxygenase - Homogentisate 1,2-dioxygenase - Cysteine dioxygenase - 4-Hydroxyphenylpyruvate dioxygenase - Indoleamine 2,3-dioxygenase - Lipoxygenase (5) |
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| 1.13.12 - one atom of oxygen | Firefly luciferase |
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| 1.13.99 - other | Inositol oxygenase |
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| Oxidoreductases: dioxygenases, including steroid hydroxylases (EC 1.14) |
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| 1.14.11 - 2-oxoglutarate | Prolyl hydroxylase - Lysyl hydroxylase |
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| 1.14.13 - NADH or NADPH | Flavin-containing monooxygenase - Nitric oxide synthase - Cholesterol 7 alpha-hydroxylase - Methane monooxygenase - 3A4 -51A1 |
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| 1.14.14 - reduced flavin or flavoprotein | 19A1 - 2D6 - 2E1 |
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| 1.14.15 - reduced iron-sulfur protein | 11B1 - 11B2 - 11A1 |
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| 1.14.16 - reduced pteridine | Phenylalanine hydroxylase - Tyrosine hydroxylase - Tryptophan hydroxylase |
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| 1.14.17 - reduced ascorbate | Dopamine beta hydroxylase |
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| 1.14.18-19 - other | Tyrosinase - Stearoyl-CoA desaturase-1 |
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| 1.14.99 - miscellaneous | Cyclooxygenase - Heme oxygenase (HMOX1) - Squalene monooxygenase - 17A1 - 21A2 |
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