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In biochemistry, an oxidoreductase is an
enzyme Enzymes () are proteins that act as biological catalysts (biocatalysts). Catalysts accelerate chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates int ...
that catalyzes the transfer of electrons from one molecule, the reductant, also called the electron donor, to another, the oxidant, also called the electron acceptor. This group of enzymes usually utilizes NADP+ or NAD+ as cofactors. Transmembrane oxidoreductases create
electron transport chain is the site of oxidative phosphorylation in eukaryotes. The NADH and Succinic acid, succinate generated in the citric acid cycle are oxidized, providing energy to power ATP synthase. Image:Thylakoid membrane 3.svg, 400px, Photosynthetic electron tr ...

electron transport chain
s in bacteria, chloroplasts and
mitochondria
mitochondria
, including respiratory complexes I,
II
II
and
III
III
. Some others can associate with biological membranes as peripheral membrane proteins or be anchored to the membranes through a single transmembrane helix.Superfamilies of single-pass transmembrane oxidoreductases
in Membranome database


Reactions

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: :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 oxygen, O2 is the acceptor.


Classification

Oxidoreductases are classified as EC 1 in the Enzyme Commission number, EC number classification of enzymes. Oxidoreductases can be further classified into 21 subclasses: *:EC 1.1, EC 1.1 includes oxidoreductases that act on the CH-OH group of donors (alcohol oxidoreductases) *:EC 1.2, EC 1.2 includes oxidoreductases that act on the aldehyde or oxo group of donors *:EC 1.3, EC 1.3 includes oxidoreductases that act on the CH-CH group of donors (CH-CH oxidoreductases) *:EC 1.4, EC 1.4 includes oxidoreductases that act on the CH-NH2 group of donors (Amino acid oxidoreductases, Monoamine oxidase) *:EC 1.5, EC 1.5 includes oxidoreductases that act on CH-NH group of donors *:EC 1.6, EC 1.6 includes oxidoreductases that act on NADH or NADPH *:EC 1.7, EC 1.7 includes oxidoreductases that act on other nitrogenous compounds as donors *:EC 1.8, EC 1.8 includes oxidoreductases that act on a sulfur group of donors *:EC 1.9, EC 1.9 includes oxidoreductases that act on a heme group of donors *:EC 1.10, EC 1.10 includes oxidoreductases that act on benzenediol, diphenols and related substances as donors *:EC 1.11, EC 1.11 includes oxidoreductases that act on peroxide as an acceptor (peroxidases) *:EC 1.12, EC 1.12 includes oxidoreductases that act on hydrogen as donors *:EC 1.13, EC 1.13 includes oxidoreductases that act on single donors with incorporation of molecular oxygen (oxygenases) *:EC 1.14, EC 1.14 includes oxidoreductases that act on paired donors with incorporation of molecular oxygen *:EC 1.15, EC 1.15 includes oxidoreductases that act on superoxide radicals as acceptors *:EC 1.16, EC 1.16 includes oxidoreductases that oxidize metal ions *:EC 1.17, EC 1.17 includes oxidoreductases that act on CH or CH2 groups *:EC 1.18, EC 1.18 includes oxidoreductases that act on iron-sulfur proteins as donors *:EC 1.19, EC 1.19 includes oxidoreductases that act on reduced flavodoxin as a donor *:EC 1.20, EC 1.20 includes oxidoreductases that act on phosphorus or arsenic in donors *:EC 1.21, EC 1.21 includes oxidoreductases that act on X-H and Y-H to form an X-Y bond


See also

* Hydroxylase * List of enzymes


References


External links

*
EC 1 Introduction
from the Department of Chemistry at Queen Mary, University of London {{Portal bar, Biology, border=no Oxidoreductases, Bioinorganic chemistry