As a strong inhibitor of acrosin, it is required for normal spermiogenesis. It probably hinders premature activation of proacrosin and other proteases, thus preventing the cascade of events leading to spermiogenesis defects . May be involved in the regulation of serine protease-dependent germ cell apoptosis (By similarity). It also inhibits trypsin.
Subcellular locations: Secreted, Cytoplasmic vesicle, Secretory vesicle, Acrosome
Expressed in epididymis (at protein level).