Aldehyde oxidase
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Date: 2022-01-09

Aldehyde oxidase, by Wikipedia https://en.wikipedia.org/wiki?curid=10037951 / CC BY SA 3.0

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Aldehyde oxidase （AO） is a metabolizing enzyme, located in the cytosolic compartment of tissues in many organisms.
AO catalyzes the oxidation of aldehydes into carboxylic acid, and in addition, catalyzes the hydroxylation of some heterocycles.
It can also catalyze the oxidation of both cytochrome P450 （CYP450） and monoamine oxidase （MAO） intermediate products.
AO plays an important role in the metabolism of several drugs.
AO catalyzes the conversion of an aldehyde in the presence of oxygen and water to an acid and hydrogen peroxide.
Though the enzyme uses molecular oxygen as an electron acceptor, the oxygen atom that is incorporated into the carboxylate product is
from water; however, the exact mechanism of reduction is still not known for AO. The AO also catalyzes the oxidation of heterocycles,
which involves a nucleophilic attack located at the carbon atom beside the heteroatom.
This means that susceptibility to nucleophilic attack of a heterocycle determines if that heterocycle is a suitable substrate for AO. Aldehyde oxidase
is a member of the molybdenum flavoprotein family and has a very complex evolutionary profile—as the genes of AO varies according to animal species.
Higher primates, such as humans, have a single functioning AO gene （AOX1）, whereas rodents have four separate AOX genes.
The human population has both functionally inactive hAOX1 allelic variants and encoding enzyme variants with different catalytic activities.
AO activity has been found to be much more active in higher primates （compared to rodents）, though many factors may affect this activity, such as gender, age, cigarette smoking, drug usage, and disease states.
Aldehyde oxidase is very concentrated in the liver, where it oxidizes multiple aldehydes and nitrogenous heterocyclic compounds, such as anti-cancer and immunosuppressive drugs.
Some AO activity has been...