Identification of trypsin‐like activity in sturgeon spermatozoa

We documented amidase activity in lake sturgeon (Acipenser fulvescens) and white sturgeon (Acipenser transmontanus) spermatozoa. This activity was inhibited by benzamidine and soybean trypsin inhibitor (SBTI), and N‐α‐p‐tosyl‐L‐lysine chloromethyl ketone‐HCl (TLCK), but not by N‐tosyl‐L‐phenylalanine chloromethyl keton (TPCK), indicating the presence of trypsin‐like activity in sturgeon spermatozoa. Higher activity occurred at pH 8.5 and 9.0 than at 8.0. No effect of 10 mM KCl and 100 mM NaCl on trypsin‐like activity was found. Calcium ions inhibited the activity at 10 and 50 mM. Similar activities were documented in neat semen and washed sperm suspension. Presence of trypsin‐like activity corresponds to the presence of acrosomes and acrosome reaction in spermatozoa of these fishes.