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 (By similarity). On the 2D-gel the determined pI of this protein is: 5.3, its MW is: 16.8 kDa. Belongs to the glycosyl hydrolase 22 family. May lack the conserved Glu and Asp residues essential for activity.