A SERINE PROTEINASE IN THE PENETRATION GLANDS OF THE HEXACANTHS OF HYMENOLEPIS-DIMINUTA (CESTODA, CYCLOPHYLLIDEA)

Histochemically demonstrable activity of a serine proteinase was detec ted in the penetration glands of Hymenolepis diminuta hexacanths. At t he optimal pH of 8.4 the enzyme hydrolyzed N-blocked L-aminoacyl- and N-blocked L-peptidyl-naphthylamides bearing L-arginine at the P-1 subs ite. The proteinase did not require either Ca2+ or Mg2+ for its activi ty and was insensitive to 1 mM EGTA and 1 mM EDTA. Organic fluorophosp hates inhibited it, whereas thiol-blocking compounds did not. At opera tive pH values of 4.8 and 3.8 generated during electrophoresis in a st acking and a resolving gel, respectively, the proteinase migrated towa rd the cathode. When examined for proteolytic activity at the optimal pH of 8.4, the separated enzyme produced a single band of gelatinolysi s in a gelatin-containing polyacrylamide gel. During in vitro maintena nce of the hexacanths, the secretion from their penetration glands for med a mucous cyst surrounding the individual larvae. The cyst was resi stant to and protected the hexacanths from the proteolytic activity of trypsin, papain, and proteinases extracted from the gut of the beetle Tenebrio molitor (the host). Hexacanths extracted from the hemocoel o f T. molitor at 24 and 48 h after infection were surrounded by similar mucous cysts. Consequently, roles in penetration and protection for t he secretion from the penetration glands are postulated.