Reaction: xanthine + H2O + O2 = urate + H2O2
For reaction pathway click here.
Glossary: 4-mercuribenzoate = (4-carboxylatophenyl)mercury
Other name(s): hypoxanthine oxidase; hypoxanthine:oxygen oxidoreductase; Schardinger enzyme; xanthine oxidoreductase; hypoxanthine-xanthine oxidase; xanthine:O2 oxidoreductase; xanthine:xanthine oxidase
Systematic name: xanthine:oxygen oxidoreductase
Comments: An iron-molybdenum flavoprotein (FAD) containing [2Fe-2S] centres. Also oxidizes hypoxanthine, some other purines and pterins, and aldehydes (i.e. possesses the activity of EC 1.2.3.1, aldehyde oxidase). Under some conditions the product is mainly superoxide rather than peroxide: RH + H2O + 2 O2 = ROH + 2 O2•- + 2 H+. The enzyme from animal tissues can be converted into EC 1.17.1.4, xanthine dehydrogenase. That from liver exists in vivo mainly as the dehydrogenase form, but can be converted into the oxidase form by storage at -20 °C, by treatment with proteolytic enzymes or with organic solvents, or by thiol reagents such as Cu2+, N-ethylmaleimide or 4-mercuribenzoate. The effect of thiol reagents can be reversed by thiols such as 1,4-dithioerythritol. EC 1.17.1.4 can also be converted into this enzyme by EC 1.8.4.7, enzyme-thiol transhydrogenase (glutathione-disulfide) in the presence of glutathione disulfide. The Micrococcus enzyme can use ferredoxin as acceptor.
Links to other databases: BRENDA, EXPASY, KEGG, PDB, UM-BBD, CAS registry number: 9002-17-9
References:
1. Avis, P.G., Bergel, F. and Bray, R.C. Cellular constituents. The chemistry of xanthine oxidase. Part I. The preparation of a crystalline xanthine oxidase from cow's milk. J. Chem. Soc. (Lond.) (1955) 1100-1105.
2. Battelli, M.G. and Lorenzoni, E. Purification and properties of a new glutathione-dependent thiol:disulphide oxidoreductase from rat liver. Biochem. J. 207 (1982) 133-138. [PMID: 6960894]
3. Bray, R.C. Xanthine oxidase. In: Boyer, P.D., Lardy, H. and Myrbäck, K. (Eds.), The Enzymes, 2nd ed., vol. 7, Academic Press, New York, 1963, pp. 533-556.
4. Della Corte, E. and Stirpe, F. The regulation of rat liver xanthine oxidase. Involvement of thiol groups in the conversion of the enzyme activity from dehydrogenase (type D) into oxidase (type O) and purification of the enzyme. Biochem. J. 126 (1972) 739-745. [PMID: 4342395]
5. Carpani, G., Racchi, M., Ghezzi, P., Terao, M. and Garattini, E. Purification and characterization of mouse liver xanthine oxidase. Arch. Biochem. Biophys. 279 (1990) 237-241. [PMID: 2350174]
6. Eger, B.T., Okamoto, K., Enroth, C., Sato, M., Nishino, T., Pai, E.F. and Nishino, T. Purification, crystallization and preliminary X-ray diffraction studies of xanthine dehydrogenase and xanthine oxidase isolated from bovine milk. Acta Crystallogr. D Biol. Crystallogr. 56 (2000) 1656-1658. [PMID: 11092937]