Effects of gossypol acetic acid on heart mitochondrial membranes ATPase

Gossypol exerted an inhibitory action on the mitochondrial ATPase of pig heart. The inhibition was increased either with increasing the concentration of gossypol or prolonging the incubation time. However, the ATPase activity was not longer changed after 15 min incubation at 37。C. It showed that gossypol 2.5-100 vmol/L inhibited the ATPase activity by 13-93% with 25 vmol/L of Ki value. Meanwbile, the ATPase activity was increased following increasing the concentration enzyme protein in the of absence or presence of gossypol 40 or 80 vmol/L in the reaction system. The optimal pH value for the ATPase was shifted slightly to alkali by gossypol. The kinetic analysis showed that the inhibition type of the myocardial mitochondria ATPase by gossypol was noncompetitive with ATP and Mg2+, the Ki value was 2.0 and 0.37 mmol/L, respectively. These results imply that gossypol may form an inactive complex with the enzyme-ATP.