Competitive inhibition of phospholipase A2 in vesicles.

Kinetic studies with phospholipase A2 are complicated by the fact that binding of the enzyme to the interface precedes catalytic turnover. This difficulty can be overcome by monitoring interfacial catalysis in the scooting mode where the enzyme does not leave the interface. The kinetics of inhibition by transition-state analogues shows that specific competitive inhibition is the result of competition between inhibitor and substrate for the binding to the active site of the enzyme in the interface. Several lipophilic compounds, including alkanols, substituted butyrophenones, aristolochic acid, and mepacrine apparently reduce the rate of lipolysis by promoting the desorption of phospholipase A2 from the interface.