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 and ...

, an oxidoreductase is an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

that catalyzes the transfer of

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no kn ...

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 commonly reducing agents include the Earth meta ...

, also called the

electron donor In chemistry, an electron donor is a chemical entity that donates electrons to another compound. It is a reducing agent that, by virtue of its donating electrons, is itself oxidized in the process. Typical reducing agents undergo permanent chem ...

, 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 " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...

, also called the

electron acceptor An electron acceptor is a chemical entity that accepts electrons transferred to it from another compound. It is an oxidizing agent that, by virtue of its accepting electrons, is itself reduced in the process. Electron acceptors are sometimes mista ...

. 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 aden ...

as cofactors. Transmembrane oxidoreductases create

electron transport chain 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 th ...

s in bacteria,

chloroplasts A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, ...

and

mitochondria A mitochondrion (; ) is an organelle found in the Cell (biology), cells of most Eukaryotes, such as animals, plants and Fungus, fungi. Mitochondria have a double lipid bilayer, membrane structure and use aerobic respiration to generate adenosi ...

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

biological membranes A biological membrane, biomembrane or cell membrane is a selectively permeable membrane that separates the interior of a cell from the external environment or creates intracellular compartments by serving as a boundary between one part of the ce ...

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) is a membrane-spanning protein domain. TMDs generally adopt an alpha helix topological conformation, although some TMDs such as those in porins can adopt a different conformation. Because the interior of the lipid bi ...

.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, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction ...

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

glycolysis Glycolysis is the metabolic pathway that converts glucose () into pyruvate (). The free energy released in this process is used to form the high-energy molecules adenosine triphosphate (ATP) and reduced nicotinamide adenine dinucleotide (NADH ...

: :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 metabolic pathway, pathways of all o ...

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 f ...

" 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 enzyme that catalyzes oxidation-reduction reactions, especially one involving dioxygen (O2) as the electron acceptor. In reactions involving donation of a hydrogen atom, oxygen is reduced to water (H2O) or hydro ...

" 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 a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The ...

) * EC 1.2 includes oxidoreductases that act on the

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...

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 Amino acid oxidoreductases are oxidoreductases, a type of enzyme, that act upon amino acids. They constitute the majority of enzymes classified under EC number 1.4, with most of the remainder being monoamine oxidases. Examples include: * Glutama ...

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 first ...

) * 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 Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...

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

heme Heme, or haem (pronounced / hi:m/ ), is a precursor to hemoglobin, which is necessary to bind oxygen in the bloodstream. Heme is biosynthesized in both the bone marrow and the liver. In biochemical terms, heme is a coordination complex "consisti ...

group of donors * EC 1.10 includes oxidoreductases that act on

diphenol Diphenol may refer to: * Benzenediols * Bisphenols * Dihydroxybiphenyls * Certain polyphenol Polyphenols () are a large family of naturally occurring organic compounds characterized by multiples of phenol units. They are abundant in plants an ...

s and related substances as donors * EC 1.11 includes oxidoreductases that act on

peroxide In chemistry, peroxides are a group of compounds with the structure , where R = any element. The group in a peroxide is called the peroxide group or peroxo group. The nomenclature is somewhat variable. The most common peroxide is hydrogen p ...

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. Functionality Peroxidases typically ca ...

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 (

oxygenase An oxygenase is any enzyme that oxidizes a substrate by transferring the oxygen from molecular oxygen O2 (as in air) to it. The oxygenases form a class of oxidoreductases; their EC number is EC 1.13 or EC 1.14. Discoverers Oxygenases were disco ...

s) * 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 the ...

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 Flavodoxins (Fld) are small, soluble electron-transfer proteins. Flavodoxins contains flavin mononucleotide as prosthetic group. The structure of flavodoxin is characterized by a five-stranded parallel beta sheet, surrounded by five alpha helices. T ...

as a donor * EC 1.20 includes oxidoreductases that act on

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...

arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, but ...

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 , mottoeng = With united powers , established = 1785 – The London Hospital Medical College1843 – St Bartholomew's Hospital Medical College1882 – Westfield College1887 – East London College/Queen Mary College , type = Public researc ...

{{Portal bar, Biology, border=no Bioinorganic chemistry

Reactions

Nomenclature

Classification

See also

References

External links