Inactivation of the mitochondrial adenosine triphosphatase from Trypanosoma cruzi by oxygen radicals: role of thiol groups.
Inactivation of Trypanosoma cruzi mitochondrial ATPase by oxygen radicals, generated by redox cycling of the ascorbate-Cu system (Cataldi de Flombaum, M.A. and Stoppani, A.O.M. (1986) Biochem. Int. 12, 785-793), involves oxidation of the enzyme thiols, as indicated by the competitive kinetics obtained with p-chloromercuribenzoate, a selective SH-reagent. Dithiothreitol prevented the ascorbate-Cu effect but did not reactivate the enzyme. Non-competitive kinetics were obtained with ascorbate-Cu and increasing MgATP concentration, or with phenylglyoxal, as second inhibitor. Since phenylglyoxal reacts with arginyl residues at the ATPase hydrolytic site, these results suggest that the oxgen-sensitive thiols were located outside the hydrolytic site.
Cataldi de Flombaum
M A
MA
Centro de Investigaciones Bioenergéticas, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
Stoppani
A O
AO
D000251:Adenosine Triphosphatases / Q000032:analysis / Q000037:antagonists & inhibitors*; D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology; D003300:Copper / Q000494:pharmacology; D008928:Mitochondria / Q000201:enzymology*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000494:pharmacology*; D013438:Sulfhydryl Compounds / Q000032:analysis / Q000502:physiology*; D014349:Trypanosoma cruzi / Q000201:enzymology*
D013438:Sulfhydryl Compounds; D003300:Copper; D000251:Adenosine Triphosphatases; D001205:Ascorbic Acid; D010100:Oxygen