Sperm acrosome membrane-associated protein 3 (SPACA3)

Sperm acrosome membrane-associated protein 3 (SPACA3, also known as SLLP1/SPRASA) is a sperm-specific, lysozyme-like protein localized to the acrosomal matrix of human sperm. Despite strong structural similarity to conventional lysozymes, it lacks catalytic bacteriolytic activity and instead is implicated in the adhesion and binding to egg extracellular matrix carbohydrates (notably N-acetylglucosamine), promoting sperm–oocyte interaction during fertilization. SPACA3 is expressed almost exclusively in testis and sperm, with aberrant expression observed in some cancers, qualifying it as a cancer-testis antigen. Variant forms and immunoreactivity have also been associated with male and female infertility, with additional roles in ovarian follicle and corpus luteum biology.

Other names

SLLP1SPRASAALLP17CT54LYC3LYZCLYZL3Cancer/testis antigen 54Sperm lysozyme-like protein 1Lysozyme-like protein 3Lysozyme-like acrosomal sperm-specific secretory protein ALLP-17Sperm protein reactive with antisperm antibodies