RESUMO
Activity of H(+)-ATPase of Trypanosoma cruzi (RA strain) submitochondrial particles is increased in parasites which have a low spermine content caused by growing in a polyamine free medium or in a medium containing inhibitors of polyamine synthesis. Under these conditions, the proliferation rate is markedly decreased. Kinetics of the enzyme inhibition by spermine indicates a non-competitive inhibition. Spermine, through its action on the H(+)-ATPase hydrophobic environment, affects the enzyme activity. Together with the ATPase protein inhibitor, this could be a mechanism regulating ATP levels needed for the parasite proliferation.
Assuntos
Mitocôndrias/enzimologia , ATPases Translocadoras de Prótons/metabolismo , Espermina/farmacologia , Trypanosoma cruzi/enzimologia , Trypanosoma cruzi/crescimento & desenvolvimento , Animais , Cicloeximida/farmacologia , Eflornitina/farmacologia , Cinética , ATPases Translocadoras de Prótons/efeitos dos fármacos , Putrescina/metabolismo , Espermidina/metabolismo , Espermina/metabolismo , Partículas Submitocôndricas/enzimologia , Trypanosoma cruzi/efeitos dos fármacosRESUMO
ATP hydrolysis by Crithidia fasciculata mitochondrial ATPase was studied through the use of submitochondrial particles and the soluble enzyme. (a) ATP hydrolysis by these preparations was inhibited by spermine but not by spermidine or putrescine. (b) The ATPase activity inhibited by spermine was partially recovered when excess Mg2+ was added to the reaction mixture. (c) When polyamines were present throughout the preparation of the mitochondrial membranes, the membrane-bound ATPase was irreversibly inactivated. The polyamine effect decreased in the order spermine > putrescine > spermidine. (d) The spermidine or putrescine pre-treated membranes oxidized succinate at a faster rate than the control ones. (e) Trypanosoma cruzi F-ATPase was inhibited by polyamines in the same manner as the C. fasciculata enzyme.
Assuntos
Adenosina Trifosfatases/metabolismo , Crithidia fasciculata/efeitos dos fármacos , Mitocôndrias/efeitos dos fármacos , Poliaminas/farmacologia , Trypanosoma cruzi/efeitos dos fármacos , Animais , Crithidia fasciculata/enzimologia , Hidrólise , Cinética , Magnésio/farmacologia , Mitocôndrias/enzimologia , Putrescina/farmacologia , Espermidina/farmacologia , Espermina/farmacologia , Trypanosoma cruzi/enzimologiaRESUMO
An inhibitor of Crithidia fasciculata and Trypanosoma cruzi H+ -ATP synthase (ATPase) was isolated from these organims mitochondrial particles, either by (a) ammonium sulfate-cholate extraction followed by heat treatment and ethanol precipitation, or (b) gel-filtration on Sephadex G-50, followed by a similar purification procedure. Inactivation by trypsin supported the inhibitor peptide structure. Removal of the peptide inhibitor increased about three-fold the specific activity of the protozoan ATPases. The isolated peptides and a highly purified bovine heart ATPase inhibitor inhibited C. fasciculata ATPase as a function of the peptide concentration.