MetaCyc Biological-Roles Class: a reduced two electron carrier

Synonyms: a reduced unknown two electron donor, A(H2), a reduced unknown two electron acceptor

Summary:
In general, an electron carrier is a chemical entity that can accept or donate electrons from/to another chemical entity. When accepting electrons, it acts as an "electron acceptor". By accepting the electrons, the acceptor is reduced, and thus prior to receiving the electrons the entity is called "an oxidized electron acceptor" and after receiving them it is called "a reduced electron acceptor".

Many reduced electron acceptors are able to transfer the electrons to other molecules, becoming oxidized in the process. Thus the distinction between an electron acceptor and an electron donor is often not determined by the actual chemical entity, but by the role it plays in a particular reaction. However, some acceptors in biological reactions only accept electrons and do not transfer them further. Those are often known as "terminal electron acceptors".

While in general every chemical reaction in which electrons are transferred includes an electron donor and an electron acceptor, several molecules are commonly used in metabolism solely for the purpose of electron transfer, and are referred to in biology as electron carriers. Different biological electron carriers differ in the number of electrons that they transfer and in their electron affinity.

Some of the common biological electron carriers transfer only a single electron (e.g. , , and some ), some transfer two electrons (e.g. some ), some transfer a hydride ion ( e.g. and ), and some transfer two electrons and two protons ( , and ). In addition, a number of inorganic small molecules (e.g. oxygen, nitrate, iron (III), manganese (IV), sulfate) are often used as terminal electron acceptors.

In many cases, purified enzymes can act in vitro using an artificial electron carrier, and their in vivo electron carrier is not known. The classes of "unknown electron carriers" are used to describe such reactions, which are incompletely characterized.

Parent Classes

ChEBI17499
KeggC00030
MetaNetXMNXM36
Seedcpd26978

Ontology Diagram

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Reactions known to both consume and produce the compound:

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Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 46(D1):D633-D639 2018
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