Plays a role in male fertility. May have a role in sperm migration or binding to zona-intact eggs. Involved in the activation of the proacrosin/acrosin system. Belongs to the peptidase S1 family. Although related to peptidase S1 family, lacks the conserved active Ser residue in position 192 which is replaced by an Ala, suggesting that it has no protease activity. Lacks also metal binding sites Glu in position 67 which is replaced by Asn and Asn in position 69 which is replaced by Arg.