Superoxide xanthine oxidase

Table 9.6 Examination of Superoxide Involvement in the Chemiluminescence of PM-2 Elicited by the Fe2+-H2C>2 System and the Xanthine-Xanthine Oxidase System3 (Shimomura, 1991b)...

Storch, J., and Ferber, E. (1988). Detergent-amplified chemiluminescence of lucigenin for determination of superoxide anion production by NADPH oxidase and xanthine oxidase. Anal. Biochem. 169 262-267. 

Superoxide is formed when reduced flavins—present, for example, in xanthine oxidase—are reoxidized univalently by molecular oxygen. 

Superoxide is formed (reaction 1) in the red blood cell by the auto-oxidation of hemoglobin to methemo-globin (approximately 3% of hemoglobin in human red blood cells has been calculated to auto-oxidize per day) in other tissues, it is formed by the action of enzymes such as cytochrome P450 reductase and xanthine oxidase. When stimulated by contact with bacteria, neutrophils exhibit a respiratory burst (see below) and produce superoxide in a reaction catalyzed by NADPH oxidase (reaction 2). Superoxide spontaneously dismu-tates to form H2O2 and O2 however, the rate of this same reaction is speeded up tremendously by the action of the enzyme superoxide dismutase (reaction 3). Hydrogen peroxide is subject to a number of fates. The enzyme catalase, present in many types of cells, converts... 

It is possible that dietary flavonoids participate in the regulation of cellular function independent of their antioxidant properties. Other non-antioxidant direct effects reported include inhibition of prooxidant enzymes (xanthine oxidase, NAD(P)H oxidase, lipoxygenases), induction of antioxidant enzymes (superoxide dismutase, gluthathione peroxidase, glutathione S-transferase), and inhibition of redox-sensitive transcription factors. 

Kellogg, E.W. and Fridovich, I. (1975). Superoxide, hydrogen peroxide, and singlet oxygen in lipid peroxidation by a xanthine oxidase system. J. Biol. Chem 250, 8812-8817. 

Roy, R.S. and McCord, J.M. (1983). Superoxide and ischaemia conversion of xanthine dehydrogenase to xanthine oxidase. In Oxyradicals and their Scavenging Systems , Vol. 2 (eds. K Greenwald and G. Cohen) pp. 145-153. Elsevier, New York. 

Biemond, P., Swaak, A.J.G., BiendorfF, C.M., and Kostner, J.F. (1986). Superoxide-dependent and independent mechanisms of iron mobilisation from ferritin by xanthine oxidase. Biochem. J. 239, 169-173. 

Fridovich, I. (1970). Quantitative aspects of the production of superoxide anion radical by milk xanthine oxidase. J. Biol. Chem. 245, 4053-4057. 

Pence, B.C. and Naylor, M.F. (1990). Effect of single-dose ultraviolet radiation on skin superoxide dismutase, catalase and xanthine oxidase in hairless mice. J. Invest. Dermatol. 95, 213-216. 

Porras, A.G., Olson, J.S. and Palmer, G. (1981). The reaction of reduced xanthine oxidase with oxygen kinetics of peroxide and superoxide formation. J. Biol. Chem. 256, 9096-9103. 

Nonaka, A., Manabe, T., Tamura, K., Asano, N., Imanishi, K. and Tobe, T. (1989b). Changes of xanthine oxidase, lipid peroxide and superoxide dismutase in mouse acute pancreatitis. Digestion 43, 41-46. 

Ariza ME, Bijur GN, Williams MV. 1998. Lead and mercury mutagenesis Role of H202, superoxide dismutase, and xanthine oxidase. Environ Mol Mut 31 352-361. 

K.V. Gobi, Y. Sato, and F. Mizutani, Mediatorless superoxide dismutase sensors using cytochrome c-modified electrodes xanthine oxidase incorporated polyion complex membrane for enhanced activity and in-vivo analysis. Electroanalysis 13, 397-403 (2001). 

The release of iron from ferritin can be induced by different factors. In 1984, Biemond et al. [159] have shown that stimulated leukocytes mobilize iron from human and horse ferritin. Release of iron was induced by superoxide because SOD inhibited this process. Similarly, the release of iron from ferritin can be induced by xanthine oxidase [160] this process is believed to induce ischemia and inflammation. Under anerobic conditions xanthine oxidase is also able to stimulate iron release from ferritin through superoxide-independent mechanism [161]. Another physiological free radical nitric oxide also stimulates iron release from ferritin [162],... 

The mechanism of iron-initiated superoxide-dependent lipid peroxidation has been extensively studied by Aust and his coworkers [15-18]. It was found that superoxide produced by xanthine oxidase initiated lipid peroxidation, but this reaction was not inhibited by hydroxyl radical scavengers and, therefore the formation of hydroxyl radicals was unimportant. Lipid peroxidation depended on the Fe3+/Fe2+ ratio, with 50 50 as the optimal value [19]. Superoxide supposedly stimulated peroxidation both by reducing ferric ions and oxidizing ferrous ions. As superoxide is able to release iron from ferritin, superoxide-promoted lipid peroxidation can probably proceed under in vivo conditions [16,20]. 

LOX-dependent superoxide production was also registered under ex vivo conditions [55]. It has been shown that the intravenous administration of lipopolysaccharide to rats stimulated superoxide production by alveolar and peritoneal macrophages. O Donnell and Azzi [56] proposed that a relatively high rate of superoxide production by cultured human fibroblasts in the presence of NADH was relevant to 15-LOX-catalyzed oxidation of unsaturated acids and was independent of NADPH oxidase, prostaglandin H synthase, xanthine oxidase, and cytochrome P-450 activation or mitochondrial respiration. LOX might also be involved in the superoxide production by epidermal growth factor-stimulated pheochromo-cytoma cells [57]. 

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