Aminopeptidase-like protease released from oocytes affects oocyte surfaces and suppresses the acrosome reaction in establishment of polyspermy block in oocytes of the mussel Mytilus edulis.
Suppression of the acrosome reaction of sperm on fertilized oocytes inhibits sperm-oocyte binding and is considered one of the three mechanisms responsible for polyspermy block in oocytes of the mussel Mytilus edulis (Togo et al., 1995). When unfertilized oocytes were inseminated in the presence of aminopeptidase inhibitors and the fertilized oocytes were inseminated again, neither the acrosome reaction nor sperm binding to fertilized oocytes were suppressed, suggesting that aminopeptidase-like protease participates in suppression of the acrosome reaction. The supernatant solution obtained after centrifuging a suspension of fertilized oocytes hydrolyzed aminopeptidase substrates, and these activities were inhibited strongly or effectively by aminopeptidase inhibitors. When unfertilized oocytes were incubated with this supernatant solution and inseminated, both the number of sperm bound and the acrosome reaction rate decreased, and these effects were reversed by conducting this treatment in the presence of aminopeptidase inhibitors. These results suggest that aminopeptidase-like protease released from the oocyte at fertilization affects the oocyte surface to suppress the acrosome reaction and consequently inhibits sperm-oocyte binding.
Togo
T
T
Misaki Marine Biological Station, University of Tokyo, Kanagawa, Japan. togot@mmbs.s.u-tokyo.ac.jp
Morisawa
M
M
D000177:Acrosome / Q000187:drug effects / Q000502:physiology*; D000626:Aminopeptidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D049872:Bivalvia; D002462:Cell Membrane / Q000502:physiology; D005260:Female; D005306:Fertilization / Q000502:physiology; D006868:Hydrolysis; D008297:Male; D009865:Oocytes / Q000201:enzymology / Q000502:physiology*; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000502:physiology
D000626:Aminopeptidases