Presence of PI-rich vesicles is required for the PLC ζ activation according to mathematical modeling

Phospholipase Cζ (PLCζ) is an enzyme found in the cytoplasm and acrosome of mammalian spermatozoa. It catalyzes the reaction of phosphatidylinositol-4,5-phosphate hydrolysis into inositol-3-phosphate and diacylglycerol. PLCζ is present in the sperm cell acrosome and cytosol but doesn’t significantly affect its metabolism. However, after the fusion of sperm and egg membranes, its activity increases as it begins to bind membranes of the egg. It is unknown why PLCζ is inactive in spermatozoa or any type of somatic cell.

In this work, the modeling approach explains the reasons for the absence of PLCζ activity in any type of mammalian cells but eggs. A model describing the activity of PLCζ in physiological calcium concentrations was developed. It was shown that the presence of phosphoinositide-rich vesicles is required for the PLCζ activity in mature mammalian eggs.