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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^–

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:

P_i + 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).

Contents 1 Nomenclature 2 Classification 3 See also 4 External links

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.

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
• EC 1.19 includes oxidoreductases that act on reduced flavodoxin as a donor
• EC 1.20 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

• List of enzymes
• hydroxylase

• EC 1 Introduction from the Department of Chemistry at Queen Mary, University of London

v • d • e Proteins: enzymes
Topics	Active site - Allosteric regulation - Binding site - Catalytically perfect enzyme - Coenzyme - Cofactor - Cooperativity - EC number Enzyme catalysis - Enzyme inhibitor - Enzyme kinetics - Lineweaver-Burk plot - Michaelis-Menten kinetics - List of enzymes
Types	EC1 Oxidoreductases/list - EC2 Transferases/list - EC3 Hydrolases/list - EC4 Lyases/list - EC5 Isomerases/list - EC6 Ligases/list

v • d • e Oxidoreductases: alcohol oxidoreductases (EC 1.1)
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
1.1.3 oxygen acceptor	Glucose oxidase - L-gulonolactone oxidase - Xanthine oxidase

v • d • e Aldehyde/oxo oxidoreductases (EC 1.2)
1.2.1 - NAD or NADP acceptor	Aldehyde dehydrogenase - Acetaldehyde dehydrogenase (ALDH2) - Glyceraldehyde 3-phosphate dehydrogenase - Long-chain-aldehyde dehydrogenase
1.2.4 - disulfide acceptor	Oxoglutarate dehydrogenase - Pyruvate dehydrogenase - Branched-chain alpha-keto acid dehydrogenase complex

v • d • e Oxidoreductases: CH-CH oxidoreductases (EC 1.3)
1.3.1. NAD/NADP acceptor	Enoyl-acyl carrier protein reductase/Enoyl ACP reductase - 7-Dehydrocholesterol reductase - Biliverdin reductase - 2,4 Dienoyl-CoA reductase
1.3.3. Oxygen acceptor	Dihydroorotate dehydrogenase - Coproporphyrinogen III oxidase - Protoporphyrinogen oxidase -
1.3.5. Quinone	Succinate - coenzyme Q reductase
1.3.99. Other acceptors	Fumarate reductase - Butyryl CoA dehydrogenase - Acyl CoA dehydrogenase - 5-alpha reductase - Glutaryl-CoA dehydrogenase - Isovaleryl coenzyme A dehydrogenase

v • d • e CH-NH2 oxidoreductases (EC 1.4) - primarily amino acid oxidoreductases
1.4.1 - NAD/NADP acceptor	Glutamate dehydrogenase (GLUD1)
1.4.3 - oxygen acceptor	D-amino acid oxidase - Amine oxidase - Lysyl oxidase - Monoamine oxidase
1.4.4 - disulfide acceptor	Glycine decarboxylase complex
1.4.99 - other acceptors	D-amino acid dehydrogenase - Amine dehydrogenase

v • d • e CH-NH oxidoreductases (EC 1.5)
1.5.1 - NAD or NADP acceptor	Dihydrofolate reductase - Saccharopine dehydrogenase - Methylenetetrahydrofolate reductase
1.5.3 - oxygen acceptor	Dihydrobenzophenanthridine oxidase - Sarcosine oxidase
1.5.5 - quinone acceptor	Electron-transferring-flavoprotein dehydrogenase

v • d • e NADH or NADPH oxidoreductases (EC 1.6)
Methemoglobin reductase - NADPH oxidase (P91-PHOX) - NADH dehydrogenase

v • d • e Oxidoreductases: nitrogenous donor (EC 1.7)
GMP reductase - Urate oxidase

v • d • e Oxidoreductases: sulfur oxidoreductases (EC 1.8)
Dihydrolipoamide dehydrogenase - Glutathione reductase - Thioredoxin reductase - Sulfite oxidase

v • d • e Diphenol family oxidoreductases (EC 1.10)
Coenzyme Q - cytochrome c reductase - Catechol oxidase - Laccase - Alternative oxidase

v • d • e Oxidoreductases: peroxidases (EC 1.11)
Catalase - Cytochrome c peroxidase - Eosinophil peroxidase - Glutathione peroxidase - Horseradish peroxidase - Lactoperoxidase - Myeloperoxidase - Thyroid peroxidase - Deiodinase (Tetraiodothyronine 5' deiodinase)

v • d • e Oxidoreductases: monooxygenases (EC 1.13)
1.13.11 - two atoms of oxygen	Catechol dioxygenase - Homogentisate 1,2-dioxygenase - Cysteine dioxygenase - 4-Hydroxyphenylpyruvate dioxygenase - Indoleamine 2,3-dioxygenase - Lipoxygenase (5)
1.13.12 - one atom of oxygen	Firefly luciferase
1.13.99 - other	Inositol oxygenase

v • d • e Oxidoreductases: dioxygenases, including steroid hydroxylases (EC 1.14)
1.14.11 - 2-oxoglutarate	Prolyl hydroxylase - Lysyl hydroxylase
1.14.13 - NADH or NADPH	Flavin-containing monooxygenase - Nitric oxide synthase - Cholesterol 7 alpha-hydroxylase - Methane monooxygenase - 3A4 -51A1
1.14.14 - reduced flavin or flavoprotein	19A1 - 2D6 - 2E1
1.14.15 - reduced iron-sulfur protein	11B1 - 11B2 - 11A1
1.14.16 - reduced pteridine	Phenylalanine hydroxylase - Tyrosine hydroxylase - Tryptophan hydroxylase
1.14.17 - reduced ascorbate	Dopamine beta hydroxylase
1.14.18-19 - other	Tyrosinase - Stearoyl-CoA desaturase-1
1.14.99 - miscellaneous	Cyclooxygenase - Heme oxygenase (HMOX1) - Squalene monooxygenase - 17A1 - 21A2

v • d • e Other oxidoreductases (EC 1.15-1.18)
1.15 - Acting on superoxide as acceptor	Superoxide dismutase
1.16 - Oxidizing metal ions	Ceruloplasmin
1.17 - Acting on CH or CH2 groups	Xanthine oxidase - Ribonucleotide reductase
1.18 - Acting on iron-sulfur proteins as donors	Nitrogenase