Nitro-oleic acid, a novel and irreversible inhibitor of xanthine oxidoreductase

KELLEY EE, BATTHYANY CI, HUNDLEY NJ, WOODCOCK SR, BONACCI G, DEL RIO JM, SCHOPFER FJ, LANCASTER JR JR, FREEMAN BA, TARPEY MM.

JOURNAL OF BIOLOGICAL CHEMISTRY

AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Año: 2008 vol. 283 p. 36176 - 36184

0021-9258

Xanthine oxidoreductase (XOR) generates proinflammatory oxidants and secondary nitrating species, with inhibition of XOR proving beneficial in a variety of disorders. Electrophilic nitrated fatty acid derivatives, such as nitro-oleic acid (OA-NO2), display anti-inflammatory effects with pleiotropic properties. Nitro-oleic acid inhibits XOR activity in a concentration-dependent manner with an IC50 of 0.6 microM, limiting both purine oxidation and formation of superoxide (O2.). Enzyme inhibition by OA-NO2 is not reversed by thiol reagents, including glutathione, beta-mercaptoethanol, and dithiothreitol. Structure-function studies indicate that the carboxylic acid moiety, nitration at the 9 or 10 olefinic carbon, and unsaturation is required for XOR inhibition. Enzyme turnover and competitive reactivation studies reveal inhibition of electron transfer reactions at the molybdenum cofactor accounts for OA-NO2-induced inhibition. Importantly, OA-NO2 more potently inhibits cell-associated XOR-dependent O2. production than does allopurinol. Combined, these data establish a novel role for OA-NO2 in the inhibition of XOR-derived oxidant formation.