The reactions catalyzed by Mo enzymes each find the product differing from the substrate by two electrons and two protons (or some multiple thereof). The coordination chemistry of Mo suggests that there is a distinct relationship between acid-base and redox properties of Mo complexes, and that a coupled electron-proton transfer (to or from substrate) may be mediated by Mo in enzymes. Each of th...

When investigating the potential for xanthine oxidase (XO)-mediated metabolism of a new chemical entity in vitro, selective chemical inhibition experiments are typically used. Most commonly, these inhibition experiments are performed using the inhibitor allopurinol (AP) and commercially prepared human liver cytosol (HLC) as the enzyme source. For reasons detailed herein, it is also a common pra...

Galactose oxidase can be used to oxidize the terminal carbon atom of lipids containing galactose or N-acetylgalactosamine, and the resultant aldehyde group can be reduced back to the original carbinol with radioactive borohydride. The efficiency of the first reaction has been investigated systematically by using [6-3H]galactosyl ceramide as substrate and measuring the amount of radioactive wate...

A new preparative procedure for bovine milk xanthine oxidase avoids exposure of the enzyme to proteases. The enzyme so obtained exhibited a molecular weight of about 300,000 as did chicken liver xanthine dehydrogenase. The former readily yielded species with a molecular weight of 150,000 in guanidine and in acid but could not be resolved into smaller subunits. Aldehyde oxidase of rabbit liver e...

A derivative of quinine formed in minced rabbit liver has been isolated by Kelsey et al. (I), and identified by Mead and Koepfli (2) as a carbostyril. Hence quinine is oxidized in liver with replacement of the hydrogen atom in position 2 of the quinoline ring by a hydroxy group. Analogous oxidation products are excreted by men receiving the four principal cinchona alkaloids. This change is impo...

Aldehyde oxidase (EC 1.2.3.1) has been purified by a modification of a previously reported procedure and the FAD prosthetic group has been removed by treatment with calcium chloride and calcium acetate. The deflavo enzyme so obtained is devoid of Wmethylnicotinamide oxygen reductase activity but can be reconstituted by a short incubation with FAD. The different activities of native and deflavo ...

Selenium deficiency has been reported to result in an extraordinary decrease of glutathione peroxidase (GSH-Px) and, reversely, an increase of detoxifying enzymes such as glutathione-S-transferase (GST), uridine-5'-diphosphate glucuronosyltransferase (UGT), nicotinamide-dependent quinine oxidoreductase (NQO1; DT-diaphorase), and epoxide hydrolase without significantly affecting cytochrome P450 ...