In biochemistry, an oxidoreductase is an enzyme 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 chains in bacteria, chloroplasts and mitochondria, including respiratory complexes I, II and III. Some others can associate with biological membranes as peripheral membrane proteins or be anchored to the membranes through a single transmembrane helix.
For example, an enzyme that catalyzed this reaction would be an oxidoreductase:
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:
In this reaction, NAD+ is the oxidant (electron acceptor), and glyceraldehyde-3-phosphate is the reductant (electron donor).
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 O 2 is the acceptor.
Oxidoreductases are classified as EC 1 in the EC number classification of enzymes. Oxidoreductases can be further classified into 21 subclasses:
Oxidative phosphorylation or electron transport-linked phosphorylation or terminal oxidation is the metabolic pathway in which cells use enzymes to oxidize nutrients, thereby releasing chemical energy in order to produce adenosine triphosphate (ATP). In eukaryotes, this takes place inside mitochondria. Almost all aerobic organisms carry out oxidative phosphorylation. This pathway is so pervasive because it releases more energy than alternative fermentation processes such as anaerobic glycolysis.
A dehydrogenase is an enzyme belonging to the group of oxidoreductases that oxidizes a substrate by reducing an electron acceptor, usually NAD+/NADP+ or a flavin coenzyme such as FAD or FMN. Like all catalysts, they catalyze reverse as well as forward reactions, and in some cases this has physiological significance: for example, alcohol dehydrogenase catalyzes the oxididation of ethanol to acetaldehyde in animals, but in yeast it catalyzes the production of ethanol from acetaldehyde.
An electron transport chain (ETC) is a series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples this electron transfer with the transfer of protons (H+ ions) across a membrane. Many of the enzymes in the electron transport chain are membrane-bound.
Respiratory complex I, EC 220.127.116.11 is the first large protein complex of the respiratory chains of many organisms from bacteria to humans. It catalyzes the transfer of electrons from NADH to coenzyme Q10 (CoQ10) and translocates protons across the inner mitochondrial membrane in eukaryotes or the plasma membrane of bacteria.
Nicotinamide adenine dinucleotide phosphate, abbreviated NADP+ or, in older notation, TPN (triphosphopyridine nucleotide), is a cofactor used in anabolic reactions, such as the Calvin cycle and lipid and nucleic acid syntheses, which require NADPH as a reducing agent ('hydrogen source'). It is used by all forms of cellular life.
Glycerol-3-phosphate dehydrogenase (GPDH) is an enzyme that catalyzes the reversible redox conversion of dihydroxyacetone phosphate to sn-glycerol 3-phosphate.
Formate dehydrogenases are a set of enzymes that catalyse the oxidation of formate to carbon dioxide, donating the electrons to a second substrate, such as NAD+ in formate:NAD+ oxidoreductase (EC 18.104.22.168) or to a cytochrome in formate:ferricytochrome-b1 oxidoreductase (EC 22.214.171.124).
In enzymology, a sorbitol-6-phosphate dehydrogenase (EC 126.96.36.199) is an enzyme that catalyzes the chemical reaction
In enzymology, an erythrose-4-phosphate dehydrogenase (EC 188.8.131.52) is an enzyme that catalyzes the chemical reaction
In enzymology, an alcohol dehydrogenase [NAD(P)+] (EC 184.108.40.206) is an enzyme that catalyzes the chemical reaction
In enzymology, a sn-glycerol-1-phosphate dehydrogenase (EC 220.127.116.111) is an enzyme that catalyzes the chemical reaction
In enzymology, a 4-oxoproline reductase (EC 18.104.22.168) is an enzyme that catalyzes the chemical reaction
In enzymology, a mannitol-1-phosphate 5-dehydrogenase (EC 22.214.171.124) is an enzyme that catalyzes the chemical reaction
In enzymology, a mannuronate reductase (EC 126.96.36.199) is an enzyme that catalyzes the chemical reaction
In enzymology, a methanol dehydrogenase is an enzyme that catalyzes the chemical reaction:
In enzymology, a dihydrouracil dehydrogenase (NAD+) (EC 188.8.131.52) is an enzyme that catalyzes the chemical reaction
In enzymology, an enoyl-[acyl-carrier-protein] reductase (NADPH, A-specific) (EC 184.108.40.206) is an enzyme that catalyzes the chemical reaction
In enzymology, a glyceraldehyde-3-phosphate dehydrogenase (NAD(P)+) (EC 220.127.116.11) is an enzyme that catalyzes the chemical reaction
In enzymology, a glyceraldehyde-3-phosphate dehydrogenase (phosphorylating) (EC 18.104.22.168) is an enzyme that catalyzes the chemical reaction
In enzymology, a NADH dehydrogenase (quinone) (EC 22.214.171.124) is an enzyme that catalyzes the chemical reaction