Oxidoreductases;
Acting on CH or CH2 groups;
With oxygen as acceptor

xanthine:oxygen oxidoreductase

xanthine + H2O + O2 = urate + H2O2 [RN:R02107]

R02107;
(other) R00069 R01769 R07942 R07977 R07978 R07979 R08235

xanthine [CPD:C00385];
H2O [CPD:C00001];
O2 [CPD:C00007]

An iron-molybdenum flavoprotein (FAD) containing [2Fe-2S] centres. Also oxidizes hypoxanthine, some other purines and pterins, and aldehydes, but is distinct from 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 mammalian enzyme predominantly exists as an NAD-dependent dehydrogenase (EC 1.17.1.4, xanthine dehydrogenase). During purification the enzyme is largely converted to the O2-dependent xanthine oxidase form (EC 1.17.3.2). The conversion can be triggered by several mechanisms, including the oxidation of cysteine thiols to form disulfide bonds [4,5,7,10] [which can be catalysed by EC 1.8.4.7, enzyme-thiol transhydrogenase (glutathione-disulfide) in the presence of glutathione disulfide] or limited proteolysis, which results in irreversible conversion. The conversion can also occur in vivo [4,6,10].

EC 1.17.3.2 created 1961 as EC 1.2.3.2, transferred 1984 to EC 1.1.3.22, modified 1989, transferred 2004 to EC 1.17.3.2, modified 2011

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  [PMID:6960894]

Battelli MG, Lorenzoni E.

Purification and properties of a new glutathione-dependent thiol:disulphide oxidoreductase from rat liver.

Biochem. J. 207 (1982) 133-8.

3

Bray, R.C.

Xanthine oxidase.

In: Boyer, P.D., Lardy, H. and Myrback, K. (Eds.), The Enzymes, 2nd ed., vol. 7, Academic Press, New York, 1963, p. 533-556.

4  [PMID:4342395]

Corte ED, 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) 739-45.

5  [PMID:3459393]

Ikegami T, Nishino T

The presence of desulfo xanthine dehydrogenase in purified and crude enzyme preparations from rat liver.

Arch. Biochem. Biophys. 247 (1986) 254-60.

6  [PMID:3294898]

Engerson TD, McKelvey TG, Rhyne DB, Boggio EB, Snyder SJ, Jones HP

Conversion of xanthine dehydrogenase to oxidase in ischemic rat tissues.

J. Clin. Invest. 79 (1987) 1564-70.

7  [PMID:2610112]

Saito T, Nishino T, Tsushima K

Interconversion between NAD-dependent and O2-dependent types of rat liver xanthine dehydrogenase and difference in kinetic and redox properties between them.

Adv. Exp. Med. Biol. 253B (1989) 179-83.

8  [PMID:2350174]

Carpani G, Racchi M, Ghezzi P, Terao M, Garattini E.

Purification and characterization of mouse liver xanthine oxidase.

Arch. Biochem. Biophys. 279 (1990) 237-41.

9  [PMID:11092937]

Eger BT, Okamoto K, Enroth C, Sato M, Nishino T, Pai EF, 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 Pt 12 (2000) 1656-8.

10 [PMID:18513323]

Nishino T, Okamoto K, Eger BT, Pai EF, Nishino T

Mammalian xanthine oxidoreductase - mechanism of transition from xanthine dehydrogenase to xanthine oxidase.

FEBS. J. 275 (2008) 3278-89.