Phospholipase activity of sea urchin sperm: its possible involvement in membrane fusion.

Phospholipase activity of egg-water treated Arbacia punctulata and Lytechinus variegatus sperm was shown to result from the sequential action of phospholipase A and lysophospholipase. A transient burst of phospholipase A activity followed induction of the acrosome reaction with egg water. The time of appearance suggested an acrosomal localization of the enzyme. The peak activity of phospholipase A correlated with initiation of sperm-egg fusion, suggesting a role for sea urchin sperm phospholipase A in membrane fusion and/or egg activation during fertilization.