Miklos Faust

ATPase was found in 1000g, 13 000g and 80 00Og fractions from strawberry fruits. The optima pH for ATPase was the same (i.e. 6) for the 3 fractions, which also showed similar substrate specificity. However, the enzyme associated with the 80 000 g fraction showed the highest affinity for ATP and the maximum V_max/K_m value. As the fruit ripened, from the green to dark-red stage, ATPase activity in the 80 000 g fraction increased more than three times. The ATP content of the fruit pulp, which was high at the green stage, decreased as the fruit matured and ripened. Na⁺ and K⁺ slightly stimulated enzyme activity associated with the 1000 g,80 000 g and soluble fractions, whereas, Ca²⁺ and Mg²⁺ inhibited the enzyme activity in all fractions. However, the extent of inhibition due to divalent cations lessened as the fruit ripened.