Inhibition of human and bovine sperm acrosin by divalent metal ions. Possible role of zinc as a regulator of acrosin activity

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Abstract
Human and bovine spermatozoa were collected and washed repeatedly with isotonic saline to remove seminal plasma inhibitors and activate the acrosin. The acrosin activity of the cells was assayed with .alpha.-N-Benzoyl-DL-Arg-.beta.-naphthylamide (BANA). The surface-bound enzyme was not inhibited by high-MW inhibitors of trypsin but was markedly inhibited by low-MW trypsin inhibitors. Divalent metals (Zn2+, Cu2+, Hg2+, Co2+, Cd2+) were all efficient inhibitors of acrosin on the washed cells. It was shown that the removal of Zn or Cu from acrosin completely restored activity. It is proposed that the different levels of Zn in the male and female genital tract regulate acrosin activity. Aged cells released a soluble acrosin which was inhibited by serum and seminal plasma inhibitors of trypsin-like enzymes as well as by Zn ions in an identical manner to the surface-bound enzyme.