Molybdenum, flavoprotein hydroxylases

Other enzymes may also be involved in the oxidation of aldehydes, particularly aldehyde oxidase and xanthine oxidase, which belong to the molybdenum hydroxylases. These enzymes are primarily cytosolic, although microsomal aldehyde oxidase activity has been detected. They are flavoproteins, containing FAD and also molybdenum, and the oxygen incorporated is derived from water rather than molecular oxygen. Aldehyde oxidase and xanthine oxidase in fact oxidize a wide variety of substrates, both aldehydes and nitrogen containing heterocycles such as caffeine and purines (see below). Aldehyde... 

Molybdenum hydroxylases (i.e., AO and XO) are flavoproteins that contain in addition to a FAD, a pterine cofactor coordinated to a molybdenum atom, and an iron sulfur center for their catalytic activity. They catalyze the two-electron oxidation of substrates with transfer to molecular oxygen to produce H2O2, and insert an atom of oxygen from water into a wide range of N-hctcrocycies and aldehydes via two-electron redox reaction as shown in equation 1.4 ... 

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