Regulation of endogenous calcium-dependent synaptic membrane phospholipase A2.

Synaptic plasma membrane preparations from brain tissue have endogenous Ca2+-dependent phospholipase A2 activity. Characterization of this activity revealed that it was maximally active at 10(-7)-10(-5) M Ca2+ and pH 7.0. The enzyme had a Km of 62.0 microM and a Vmax of 98.0 nmol/mg/h. Calmodulin and prostaglandin F2 alpha stimulated phospholipase A2 activity, whereas prostaglandin E2, cyclic AMP and ATP were inhibitory. Addition of exogenous phospholipase A2 to synaptic plasma membrane and synaptic vesicle preparations led to their disruption and/or lysis. We suggest that Ca2+-dependent regulation of phospholipase A2 activity may be required for synaptic vesicle and synaptic plasma membrane interaction.