Regulation of arachidonate-mobilizing phospholipase A2 by phosphorylation via protein kinase C in macrophages.

Stimulation of 32P-labeled macrophages with phorbol ester caused an increase in phosphorylation of the intracellular, high molecular weight phospholipase A2. This increase in phosphorylation was accompanied by an increase in enzyme activity, but led to no detectable shift in the concentration dependence for Ca(2+)-induced activation. The phosphorylated phospholipase A2 could be dephosphorylated by treatment with acid phosphatase, and such treatment also reduced its catalytic activity. Together with previous data, these results indicate that the arachidonate-mobilizing phospholipase A2 is dually regulated by Ca2+ (membrane interaction) and by phosphorylation (catalytic activity).