Peroxynitrite formation from the simultaneous reduction of nitrite and oxygen by xanthine oxidase.
One electron reductions of oxygen and nitrite by xanthine oxidase form peroxynitrite. The nitrite and oxygen reducing activities of xanthine oxidase are regulated by oxygen with K(oxygen) 26 and 100 microM and K(nitrite) 1.0 and 1.1 mM with xanthine and NADH as donor substrates. Optimal peroxynitrite formation occurs at 70 microM oxygen with purine substrates. Kinetic parameters: V(max) approximately 50 nmol/min/mg and K(m) of 22, 36 and 70 microM for hypoxanthine, pterin and nitrite respectively. Peroxynitrite generation is inhibited by allopurinol, superoxide dismutase and diphenylene iodonium. A role for this enzyme activity can be found in the antibacterial activity of milk and circulating xanthine oxidase activity.
Millar
Timothy M
TM
Xanthine Oxidase Research Group, School of Health, University of Bath, Claverton Down, Bath BA2 7AY, UK. millart@ucalgary.ca
D000818:Animals; D002417:Cattle; D004791:Enzyme Inhibitors / Q000378:metabolism; D008892:Milk / Q000201:enzymology; D009569:Nitric Oxide / Q000378:metabolism; D009573:Nitrites / Q000378:metabolism*; D009861:Onium Compounds / Q000378:metabolism; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D030421:Peroxynitrous Acid / Q000378:metabolism*; D012235:Rhodamines / Q000737:chemistry / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D014527:Uric Acid / Q000378:metabolism; D014969:Xanthine Oxidase / Q000378:metabolism*
D004791:Enzyme Inhibitors; D009573:Nitrites; D009861:Onium Compounds; D012235:Rhodamines; D030421:Peroxynitrous Acid; D014527:Uric Acid; D009569:Nitric Oxide; C007517:diphenyleneiodonium; D013482:Superoxide Dismutase; D014969:Xanthine Oxidase; D010100:Oxygen