Enzymatic Alteration of the Ability of Mouse Egg Plasma Membrane to Interact with Sperm1

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Abstract
The effect of a variety of proteolytic, glycosidic and lipid hydrolyzing enzymes on the ability of mouse egg plasma membrane to interact with sperm was evaluated in this study. Zona-free mouse eggs were exposed to enzymes at various concentrations, washed, and inseminated; the number of sperm attached to or having penetrated the egg plasma membrane was determined at 20 and 180 min post-insemination, respectively. The proteases trypsin and chymotrypsin caused concentration-dependent reductions in both sperm attachment and sperm penetration levels when eggs were incubated at enzyme concentrations ranging from 1- to 1000 .mu.g/ml for 30 min prior to insemination. Time-course studies revealed significant inhibition of both sperm attachment and sperm penetration levels after treating zona-free eggs for 5 min at 1000 .mu.g/ml of either trypsin or chymotrypsin. Several of the phospholipases tested, including phospholipases C, D, and A2, had no inhibitory effect on sperm penetration levels, with phospholipase C and A2 (100 .mu.g/ml) causing inhibition of sperm attachment. Of the glycosidic enzymes evaluated, glucuronidase (1000 .mu.g/ml) caused significant inhibition of sperm binding but not sperm penetration, and glucosidase, galactosidase, and neuraminidase had no effect on either sperm attachment or sperm penetration. These findings indicate that the ability of the mouse egg plasma membrane to fuse with sperm can be preferentially altered by treatment with proteases.

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