The existence of a trypsin-like enzyme (TLE) in acrosomes of epididymal spermatozoa was confirmed and was further demonstrated to be present in acrosomes of ejaculated and capacitated spermatozoa. TLE rapidly removes the zona pellucida of the ovum. Extracts of acrosomes of ejaculated spermatozoa contain an inhibitor that is separated from the TLE by purification of the TLE.
The inhibitor of TLE is also present in seminal plasma. This enzyme— enzyme inhibitor relationship appears analogous to the corona-removing enzyme-decapacitation factor relationship and part of capacitation very likely involves removal of the inhibitor from TLE and decapacitation factor from the corona-removing enzyme. TLE is inhibited by soybean trypsin inhibitor and less effectively by mercaptoethanol.
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