XANTHINE OXIDOREDUCTASE CATALYZES THE REDUCTION OF NITRATES AND NITRITE TO NITRIC-OXIDE UNDER HYPOXIC CONDITIONS

Xanthine oxidoreductase (XOR) catalyses the reduction of the therapeut ic organic nitrate, nitroglycerin (glyceryl trinitrate, GTN), as well as inorganic nitrate and nitrite, to nitric oxide (NO) under hypoxic c onditions in the presence of NADH. Generation of nitric oxide is not d etectable under normoxic conditions and is inhibited by the molybdenum site-specific inhibitors, oxypurinol and (-)BOF 4272, These enzymic r eactions provide a mechanism for generation of NO under hypoxic condit ions where nitric oxide synthase does not function, suggesting a vasod ilatory role in ischaemia. (C) 1998 Federation of European Biochemical Societies.