Xanthine oxidoreductase hydroxylation reactions

Xanthine oxidoreductase and aldehyde oxidase represent a distinct class of flavin-dependent oxidases. They both dehydrogenate and hydroxylate the substrate. However, unlike the mixed-function oxideises (Section 7.3.8), the oxygen introduced into the substrate by these enzymes is derived from water, emd the role of molecular oxygen is in the reoxidation of the reduced flavin. Among other reactions, aldehyde oxidase is importemt in the oxidation of AT -methyl... 

In terms of the reaction catalyzed, molybdopterin-containing enzymes can be divided in two groups those that mediate oxygen atom transfer, such as dimethyl sulfoxide (DMSO) reductase and sulfite oxidase (SO), and those that catalyze hydroxylation reactions of aromatic heterocyclic compounds and aldehydes [116], for instance xanthine oxidoreductase (XOR) and aldehyde oxidoreductase (AOR). However, this functional classification does not coincide with structural properties that suggest that the enzymes should be grouped into five families, whose most representative members are (1) DMSO reductase (2) XOR (3) SO (4) aldehyde-... 

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