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. Belongs to the glycosyl hydrolase 22 family. Although it belongs to the glycosyl hydrolase 22 family, Thr-70 and Asn-87 are present instead of the conserved Glu and Asp which are active site residues. It is therefore expected that this protein lacks hydrolase activity.