CHYMOTRYPSIN-LIKE PROTEASE ACTIVITY ASSOCIATED WITH DEMEMBRANATED SPERM OF CHUM SALMON

Our previous study suggested that a chymotrypsin-like protease was inv olved in the motility of chum salmon sperm (Inaba K, Morisawa M, Biome d Res (1991) 12, 435-437). In this study, we examined the peptidase ac tivity of demembranated sperm of chum salmon using ten synthetic pepti des. When spermatozoa were treated with 0.040% Triton X-100 for extrac ting the plasma membrane and the suspension was separated into the Tri ton-soluble and insoluble fractions by centrifugation, only the hydrol ytic activity towards succinyl (Suc)-Leu-Leu-Val-Tyr-4-methylcoumaryl- 7-amide (MCA), a typical substrate for chymotrypsin-like protease, was mostly retained in the insoluble fraction. The bulk of the activities toward other substrates was detected in the soluble fraction. Flagell ar axonemes isolated from demembranated sperm showed considerable hydr olytic activity toward Suc-Leu-Leu-Val-Tyr-MCA and the activity was st ill retained in the axoneme even after further washing. The hydrolysis was activated by a low concentration of SDS, suggesting that the prot ease associated with the axonemes is a multicatalytic ATP-dependent pr oteinase (proteasome). Motility of demembranated sperm was inhibited b y Suc-Leu-Leu-Val-Tyr-MCA in an ATP-concentration-dependent manner. Th ese results suggest that proteasomes associated with flagellar axoneme regulate flagellar motility.