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

Abstract

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 Ca²⁺-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 Ca^2'+ (membrane interaction) and by phosphorylation (catalytic activity).