Sperm surface membrane protein that may be involved in sperm-egg plasma membrane adhesion and fusion during fertilization. It could be a potential receptor for the egg oligosaccharide residue N-acetylglucosamine, which is present in the extracellular matrix over the egg plasma membrane. The processed form has no detectable bacteriolytic activity in vitro (By similarity). Interacts with ASTL. Anterior acrosome in non-capacitated spermatozoa and retained in the equatorial segment and in the luminal face of both the inner and outer acrosomal membranes following capacitation and the acrosome reaction. The processed form derives from the membrane form by proteolytic processing. Belongs to the glycosyl hydrolase 22 family. Although it belongs to the glycosyl hydrolase 22 family, Thr-122 and Asn-139 are present instead of the conserved Glu and Asp which are active site residues. It is therefore expected that this protein lacks hydrolase activity.