The kinetic effects of in vitro phosphorylation of rabbit muscle enolase by protein kinase C. A possible new kind of enzyme regulation.

Rabbit muscle enolase was found to be phosphorylated in vitro by calcium-activated phospholipid-dependent protein kinase. The extent of incorporation (about 0.6 mol/mol subunit) and the apparent Km for the reaction (3.0 microM subunit) were determined. Kinetic studies on the unphosphorylated and phosphorylated enzymes displayed an unexpected effect of phosphorylation resulting in activation of the forward reaction and inhibition of the backward one.