Pressure variation of enzymatic reaction rates: IV. Xanthine oxidase and superoxide dismutase.
Effect of pressure on activities of O-(2)-producing enzyme xanthine oxidase (XO) and O-(2)-scavenging enzyme superoxide dismutase (SOD) has been investigated to 1000 bar. Methods used included spectrophotometric determinations of inhibition by SOD of O-(2)-induced reduction of cytochrome c and oxidation of ascorbic acids. It was found that (1) pressure increases XO activity, the activation volume being delta V not equal to = -45 +/- 5 cm3/mol; and (2) pressure decreases SOD activity, the activation volume being delta V not equal to = 30 +/- 5 cm3/mol. Under the conditions of these experiments, pressure therefore favors an increase in O-(2) activity. This may lead to increased cell damage in organisms in high-pressure situations even if oxygen concentration is held constant.
D000818:Animals; D001205:Ascorbic Acid; D002417:Cattle; D003574:Cytochrome c Group / Q000378:metabolism; D005260:Female; D007700:Kinetics; D008892:Milk / Q000201:enzymology; D011312:Pressure; D013482:Superoxide Dismutase / Q000097:blood*; D014969:Xanthine Oxidase / Q000378:metabolism*
D003574:Cytochrome c Group; D013482:Superoxide Dismutase; D014969:Xanthine Oxidase; D001205:Ascorbic Acid