Proteolysis of Specific Porcine Zona Pellucida Glycoproteins by Boar Acrosin1

The morphologic and biochemical effects on the structure and constituent glycoproteins of the zona pellucida (ZP) by a specific sperm enzyme, acrosin, and a nonsperm enzyme, trypsin, have been evaluated. Intact porcine ZP matricies, exposed to either acrosin or trypsin, were analyzed microscopically. Changes in specific glycoproteins were monitored by high-resolution two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and the silver-based color stain, GELCODE. Although these enzymes did not alter the macroscopic properties of the ZP matrix, the 2D-PAGE ZP protein patterns were markedly altered. The high molecular weight glycoprotein families (II and III) were sensitive to proteolytic digestion, whereas the major glycoprotein family (I) of the porcine zona was only partially proteolyzed by acrosin and trypsin. Furthermore, it was demonstrated that acrosin had unique substrate specificity compared to that of trypsin, since the ZP peptide patterns were found to be different. These studies are the first to demonstrate which integral glycoproteins of the native porcine ZP matrix are specifically proteolyzed by acrosin from the homologous species and that this proteolysis occurs without the dissolution of the native porcine matrix.