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Enzyme involved in redox reactions
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.
[1]
[2] 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.
[3]
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.[
citation needed]
- 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
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 such as
methanol dehydrogenase)
-
EC 1.2 includes oxidoreductases that act on the
aldehyde 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,
Monoamine oxidase)
-
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 group of donors
-
EC 1.9 includes oxidoreductases that act on a
heme 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 as an acceptor (
peroxidases)
-
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 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 or
arsenic in donors
-
EC 1.21 includes oxidoreductases that act on X-H and Y-H to form an X-Y bond
See also
References
External links
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