Doel J J, Godber B L, Eisenthal R, Harrison R
Department of Biology and Biochemistry, University of Bath, Claverton Down, BA2 7AY, Bath, UK.
Biochim Biophys Acta. 2001 Jul 2;1527(1-2):81-7. doi: 10.1016/s0304-4165(01)00148-9.
Xanthine oxidoreductase catalyses the anaerobic reduction of glyceryl trinitrate (GTN), isosorbide dinitrate and isosorbide mononitrate to inorganic nitrite using xanthine or NADH as reducing substrates. Reduction rates are much faster with xanthine as reducing substrate than with NADH. In the presence of xanthine, urate is produced in essentially 1:1 stoichiometric ratio with inorganic nitrite, further reduction of which is relatively slow. Organic nitrates were shown to interact with the FAD site of the enzyme. In the course of reduction of GTN, xanthine oxidoreductase was progressively inactivated by conversion to its desulpho form. It is proposed that xanthine oxidoreductase is one of several flavoenzymes that catalyse the conversion of organic nitrate to inorganic nitrite in vivo. Evidence for its further involvement in reduction of the resulting nitrite to nitric oxide is discussed.
黄嘌呤氧化还原酶催化甘油三硝酸酯（GTN）、异山梨醇二硝酸酯和异山梨醇单硝酸酯在无氧条件下以黄嘌呤或NADH作为还原底物还原为无机亚硝酸盐。以黄嘌呤作为还原底物时的还原速率比以NADH时快得多。在黄嘌呤存在的情况下，尿酸与无机亚硝酸盐按基本1:1的化学计量比生成，无机亚硝酸盐的进一步还原相对较慢。有机硝酸盐被证明与该酶的FAD位点相互作用。在GTN的还原过程中，黄嘌呤氧化还原酶通过转化为脱硫形式而逐渐失活。有人提出黄嘌呤氧化还原酶是几种在体内催化有机硝酸盐转化为无机亚硝酸盐的黄素酶之一。文中还讨论了其进一步参与将生成的亚硝酸盐还原为一氧化氮的证据。
