Susceptibility of protein kinase C to oxidative inactivation: Loss of both phosphotransferase activity and phorbol diester binding

Abstract

Exposure of protein kinase C to low concentrations of either N-chlorosuccinimide or H₂O₂ resulted in rapid and parallel loss of phosphotransferase activity and phorbol ester binding. This oxidative inactivation of protein kinase C also occurred in intact cells exposed to a low concentration of H₂O₂. With H₂O₂ treatment the rate of inactivation of protein kinase C in the cytosol of MCF-7 cells was rather slower than that which occurred in the cytosol of PYS cells. However, in both cell types, the oxidative inactivation of membrane-associated protein kinase C occurred rapidly in comparison to the enzyme in the cytosol. Prior treatment of cells with phorbol ester to induce membrane association (stabilization) of protein kinase C, followed by exposure to H₂O₂, resulted in increased inactivation of protein kinase C, suggesting that membrane association of protein kinase C increases its susceptibility to oxidative inactivation