Timing of action of sperm proteases in ascidian fertilization

Summary The timing of action of three sperm proteases, acrosin, spermosin, and a chymotrypsin-like enzyme, in the fertilization of the ascidian,Halocynthia roretzi, was examined by adding specific protease inhibitors at various times after insemination. The results indicate that the last two enzymes both function at the early stage of the process of sperm penetration through the egg investment, while acrosin functions at the late stage.Acknowledgments. We are indebted to Dr M. Hoshi of Tokyo Institute of Technology for his helpful discussion, and to Dr T. Someno of Nippon Kayaku Kogyo Co. for his generous gifts of Z-Val-Pro-Arg-H and leupeptin. This work was supported by Grants-in-Aid from the Ministry of Education, Science and Culture of Japan, and from Naito Research Foundation.