Further observations on the effect of isooctane on respiratory enzymes.

Recently we reported that freeze-drying or centrifugation reactivated preparations of reduced diphosphopyridine nucleotide oxidase or reduced diphosphopyridine nucleotide-cytochrome c reductase which had been previously inactivated by extraction with isooctane (1). Homogenization of the enzyme preparations with small quantities of isooctane also inhibited these enzyme systems. The inhibited preparations were reactivated by vitamin K or vitamin E or by centrifugation. Because of these results we suggested that inactivation of certain enzyme preparations by extraction with solvents was not due primarily to the removal of lipide cofactors alone, but rather that the solvent itself was acting as an inhibitory or tosic agent. The mechanism of the reversal of the inhibitory effects of isooctane by certain lipides, freeze-drying, or centrifugation was postulated to be the same, namely, displacement or removal of sufficient amounts of solvent to restore enzyme activity. The effects of isooctane and hesane on enzyme systems have been investigated further in an attempt to obtain more information on their inhibitory action.