title: Induction of the acrosome reaction in black tiger shrimp (Penaeus monodon) requires sperm trypsin-like enzyme activity.
abstract: Trypsin-like enzymes in egg water (EW), a natural acrosome reaction (AR) inducer, are known for their importance in shrimp AR. In this report, we describe a unique phenomenon of the AR of black tiger shrimp (Penaeus monodon) sperm. It was completed within 45-60 sec and comprised only the acrosomal exocytosis and depolymerization of the sperm head anterior spike. We used peptidyl fluorogenic substrates to show the presence of trypsin-like enzymes in P. monodon EW and sperm, but minimal activities of chymotrypsin-like enzymes. In sperm, these trypsin-like enzymes existed both on the sperm surface and in the acrosome. The acrosomal enzyme was revealed as a 45-kDa band by fluorogenic substrate in-gel zymography. Although EW possessed high trypsin-like enzyme activities, they were not essential for the AR induction; EW pretreated with an irreversible trypsin inhibitor, or heat-inactivated EW (HI-EW), to abolish the trypsin-like activities could still induce the AR. The HI-EW-induced AR was inhibited by the presence of a membrane impermeant soybean trypsin inhibitor (SBTI) in the sperm suspension, indicating the significance of sperm-borne trypsin-like enzymes (on the surface and/or in the acrosome) in this AR process. However, pretreatment of sperm with SBTI followed by its removal from the suspension still allowed the AR to occur within 5 min of sperm exposure to HI-EW. Since trypsin-like activity of the SBTI-pretreated sperm surface at 5 min after SBTI removal was at the minimal level, our results suggest the importance of the acrosomal trypsin-like enzyme in the AR process.
authors.affiliation: Department of Anatomy, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.
authors.forename: Hathairat
authors.initials: H
authors.lastname: Kruevaisayawan
authors.forename: Rapeepun
authors.initials: R
authors.lastname: Vanichviriyakit
authors.forename: Wattana
authors.initials: W
authors.lastname: Weerachatyanukul
authors.forename: Sitthichai
authors.initials: S
authors.lastname: Iamsaard
authors.forename: Boonsirm
authors.initials: B
authors.lastname: Withyachumnarnkul
authors.forename: Ajoy
authors.initials: A
authors.lastname: Basak
authors.forename: Nongnuj
authors.initials: N
authors.lastname: Tanphaichitr
authors.forename: Prasert
authors.initials: P
authors.lastname: Sobhon
mesh_terms: D020101:Acrosome Reaction / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D005260:Female; D008297:Male; D008954:Models, Biological; D010063:Ovum / Q000201:enzymology / Q000378:metabolism; D033561:Penaeidae / Q000502:physiology*; D010447:Peptide Hydrolases / Q000378:metabolism / Q000502:physiology; D011480:Protease Inhibitors / Q000494:pharmacology; D014357:Trypsin / Q000378:metabolism* / Q000502:physiology*
chemical_list: D011480:Protease Inhibitors; D010447:Peptide Hydrolases; D014357:Trypsin