Acrosin (ACR)

Acrosin is a serine protease enzyme (encoded by the *ACR* gene in humans) located in the acrosome of spermatozoa[1][2]. It is synthesized as an inactive zymogen (proacrosin), which becomes active during the acrosome reaction upon sperm's approach to the oocyte[1][2][3]. The active enzyme hydrolyzes proteins in the zona pellucida, the glycoprotein layer surrounding the egg, enabling sperm to penetrate and fertilize the oocyte[1][2][3]. Acrosin also assists in secondary binding of spermatozoa to the zona pellucida and dispersal of acrosomal contents. Its major role is in the mechanical and enzymatic process underpinning fertilization, and its activity is used diagnostically to assess semen quality and fertility potential[2][4]. Acrosin is structurally similar to other serine proteases, with a catalytic triad (serine, histidine, aspartate) and a charged exosite thought to interact with the zona matrix[1][3]. While crucial in reproductive biology, acrosin is not a target for approved therapeutics, but inhibition of its function (e.g., by suramin) has been reported to block fertilization[1]. Dysfunction or deficiency leads to male infertility due to impaired sperm penetration of the oocyte[2][4].

Other names

ProacrosinSPGF87

Inhibition of protease activity (exemplified by suramin and endogenous protein C inhibitor). No therapies utilize this MoA for treatment.