[26] Proacrosin

Acrosin is a serine endopeptidase which cleaves the carboxyl bond of arginyl and lysyl derivatives with a strong preference for arginine. Acrosin is located in or on the mammalian sperm acrosome, a lysosomelike structure located on the anterior portion of the sperm head, and is utilized by the spermatozoa for penetrating the zona pellucida of the ovum, which is a prerequisite for fertilization. The acrosin of several species is partially present in a zymogen form called proacrosin. Proacrosin has been partially purified from rabbit testicular tissue, rabbit epididymal sperm, and boar ejaculated sperm. This chapter discusses the assay methods, purification procedures, and properties of boar proacrosin. Proacrosin is assayed by determining the amount of acrosin activity produced from the zymogen after activation. Acrosin hydrolyzes protein, amide and ester substrates containing arginyl bonds, Acrosin hydrolysis of benzoyl-L-arginine ethyl ester (BAEE) is conveniently measured by following the initial increase in absorbance at 253 nm. The chapter details on the activation of Proacrosin in crude preparation, activation of purified proacrosin and the properties on proacrosin.