Acrosin is a typical serine proteinase with trypsin-like specificity. (wikipedia.org)
There exists a somewhat similar (27-35%) sequence identity between β-acrosin and other serine proteases such as trypsin and chymotrypsin. (wikipedia.org)
Thus, PCI has been hypothesized to have a protective role: if acrosomal enzymes were released prematurely, or if the spermatozoa was degenerated within the male reproductive tract, the high concentrations of PCI would inhibit acrosin from inflicting proteolytic damage on nearby tissues. (wikipedia.org)