Local anesthetics: a new class of partial inhibitors of mitochondrial ATPase

The following characteristics are reported for mitochondrial ATPase prepared by the chloroform extraction method: (1) The pH optimum for enzyme activity is at 8.0. (2) The neutral anesthetic benzocaine inhibits the enzyme at all pH values. (3) Reciprocal plots of 1/v versus 1/[ATP] show that inhibition by lidocaine, tetracaine, dibucaine, and chlorpromazine is noncompetitive; slope and intercept replots are hyperbolic, showing that the inhibition is partial rather than complete.