biochemistry Biochemistry, or biological chemistry, is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology, a ...

, an oxidoreductase is an

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

that catalyzes the transfer of

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

s from one molecule, the

reductant In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ). Examples of substances that are common reducing agents include hydrogen, carbon ...

, also called the

electron donor In chemistry, an electron donor is a chemical entity that transfers electrons to another compound. It is a reducing agent that, by virtue of its donating electrons, is itself oxidized in the process. An obsolete definition equated an electron dono ...

, to another, the

oxidant An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or "Electron acceptor, accepts"/"receives" an electron from a (called the , , or ''electr ...

, also called the

electron acceptor An electron acceptor is a chemical entity that accepts electrons transferred to it from another compound. Electron acceptors are oxidizing agents. The electron accepting power of an electron acceptor is measured by its redox potential. In the ...

. This group of enzymes usually utilizes

NADP+ 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 NAD ...

NAD+ Nicotinamide adenine dinucleotide (NAD) is a coenzyme central to metabolism. Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an ade ...

as cofactors. Transmembrane oxidoreductases create

electron transport chain An electron transport chain (ETC) is a series of protein complexes and other molecules which transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples th ...

s in bacteria,

chloroplasts A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...

and

mitochondria A mitochondrion () is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi. Mitochondria have a double membrane structure and use aerobic respiration to generate adenosine triphosphate (ATP), which is us ...

, including respiratory complexes I, II and III. Some others can associate with biological membranes as

peripheral membrane protein Peripheral membrane proteins, or extrinsic membrane proteins, are membrane proteins that adhere only temporarily to the biological membrane with which they are associated. These proteins attach to integral membrane proteins, or penetrate the periph ...

s or be anchored to the membranes through a single

transmembrane helix A transmembrane domain (TMD, TM domain) is a membrane-spanning protein domain. TMDs may consist of one or several alpha-helices or a transmembrane beta barrel. Because the interior of the lipid bilayer is hydrophobic, the amino acid residues in T ...

.Superfamilies of single-pass transmembrane oxidoreductases
in

Membranome database Membranome database provides structural and functional information about more than 6000 single-pass (bitopic) transmembrane proteins from ''Homo sapiens'', ''Arabidopsis thaliana'', ''Dictyostelium discoideum'', ''Saccharomyces cerevisiae'', '' ...

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 Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is t ...

reactions are sometimes more difficult to see, such as this reaction from

glycolysis Glycolysis is the metabolic pathway that converts glucose () into pyruvic acid, pyruvate and, in most organisms, occurs in the liquid part of cells (the cytosol). The Thermodynamic free energy, free energy released in this process is used to form ...

: :P_i + glyceraldehyde-3-phosphate + NAD⁺ → NADH + H⁺ + 1,3-bisphosphoglycerate In this reaction, NAD⁺ is the oxidant (electron acceptor), and

glyceraldehyde-3-phosphate Glyceraldehyde 3-phosphate, also known as triose phosphate or 3-phosphoglyceraldehyde and abbreviated as G3P, GA3P, GADP, GAP, TP, GALP or PGAL, is a metabolite that occurs as an intermediate in several central pathways of all organisms.Nelson, D ...

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 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 ...

" 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 In biochemistry, an oxidase is an oxidoreductase (any enzyme that catalyzes a redox reaction) that uses dioxygen (O2) as the electron acceptor. In reactions involving donation of a hydrogen atom, oxygen is reduced to water (H2O) or hydrogen peroxid ...

" 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 21 subclasses: * EC 1.1 includes oxidoreductases that act on the CH-OH group of donors (

alcohol oxidoreductases Alcohol oxidoreductases are oxidoreductase enzymes that act upon an alcohol functional group In organic chemistry, a functional group is any substituent or moiety (chemistry), moiety in a molecule that causes the molecule's characteristic chem ...

such as

methanol dehydrogenase In enzymology, a methanol dehydrogenase (MDH) is an enzyme that catalyzes the chemical reaction: : CH3OH \rightleftharpoons CH2O + 2 electrons + 2H+ How the electrons are captured and transported depends upon the kind of methanol dehydrogenase. T ...

) * EC 1.2 includes oxidoreductases that act on the

aldehyde In organic chemistry, an aldehyde () (lat. ''al''cohol ''dehyd''rogenatum, dehydrogenated alcohol) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred ...

or oxo group of donors *

EC 1.3 This list contains a list of Enzyme Commission number, EC numbers for the first group, EC 1, oxidoreductases, placed in numerical order as determined by the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology. A ...

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 Monoamine oxidases (MAO) () are a family of enzymes that catalyze the oxidation of monoamines, employing oxygen to clip off their amine group. They are found bound to the outer membrane of mitochondria in most cell types of the body. The fi ...

) * 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 This list contains a list of EC numbers for the first group, EC 1, oxidoreductases, placed in numerical order as determined by the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology. All official information i ...

includes oxidoreductases that act on other nitrogenous compounds as donors * EC 1.8 includes oxidoreductases that act on a

sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...

group of donors * EC 1.9 includes oxidoreductases that act on a

heme Heme (American English), or haem (Commonwealth English, both pronounced /Help:IPA/English, hi:m/ ), is a ring-shaped iron-containing molecule that commonly serves as a Ligand (biochemistry), ligand of various proteins, more notably as a Prostheti ...

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 In chemistry, peroxides are a group of Chemical compound, compounds with the structure , where the R's represent a radical (a portion of a complete molecule; not necessarily a free radical) and O's are single oxygen atoms. Oxygen atoms are joined ...

as an acceptor (

peroxidase Peroxidases or peroxide reductases ( EC numberbr>1.11.1.x are a large group of enzymes which play a role in various biological processes. They are named after the fact that they commonly break up peroxides, and should not be confused with other ...

s) * 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 In chemistry, a superoxide is a compound that contains the superoxide ion, which has the chemical formula . The systematic name of the anion is dioxide(1−). The reactive oxygen ion superoxide is particularly important as the product of t ...

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 Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...

arsenic Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is not ...

in donors * EC 1.21 includes oxidoreductases that act on X-H and Y-H to form an X-Y bond

References

External links

*
EC 1 Introduction
from the Department of Chemistry at

Queen Mary, University of London Queen Mary University of London (QMUL, or informally QM, and formerly Queen Mary and Westfield College) is a public research university in Mile End, East London, England. It is a member institution of the federal University of London. Today, ...

{{Authority control Bioinorganic chemistry

Reactions

Nomenclature

Classification

See also

References

External links