Proacrosin from Rabbit Epididymal Spermatozoa: Partial Purification and Initial Biochemical Characterization1

Abstract

Proacrosin, the zymogen form of acrosin was extracted with 0.25N H₂SO₄ from unwashed rabbit cauda epididymal spermatozoa. Sephadex G-75 column chromatography of the extract resolved two peaks of epididymal sperm proacrosin, both of which contained low amounts of acrosin prior to activation (a total of 5 percent of the final acrosin activity obtained from complete activation of proacrosin), and were free of trypsin inhibitor. The peak eluted first (peak I) represented 85 percent of the total proacrosin and had an apparent molecular weight (MW) of 73,000 as determined by Sephadex G-100 column chromatography. Complete "autoactivation" of sperm proacrosin peak I resulted in the production of an acrosin with a MW of 38,000. Proacrosin was also found in washed epididymal sperm uncontaminated by free cytoplasmic droplets or epididymal fluid.