A serine proteinase in the penetration glands of the cercariae of Plagiorchis elegans (trematoda, plagiorchiidae)

Abstract

Cercariae of Plagiorchis elegans secrete a serine proteinase from their penetration glands. The enzyme hydrolyzes both azocoll and gelatin at the optimal pH of 8.4 but is incapable of hydrolyzing elastin at the pH range of 7.2-10.0 Ca2+ and Mg2+ activate it, whereas metal chelators (1 mM EGTA, 1 mM EDTA) and serine proteinase inhibitors (1 mM PMSF and 0.1 mM DFP) act as strong inhibitors. The proteinase activity is insensitive to thiol-blocking compounds and to 5 mM 1,10-phenanthroline, a relatively specific chelator of zinc. It appears, therefore, that the active proteinase represents a metalenzyme complex rather than a metalloenzyme. Being capable of hydrolyzing N-blocked L-alanine-1-naphthylester, N-blocked L-methionine-1-naphthylester, and naphthyl AS-D chloroacetate at pH 6.8, the proteinase is insensitive to 1 mM p-nitrophenyl phosphate, an inhibitor of some mammalian esterproteinases. The enzyme does not split N-blocked DL-phenylalanine-2-naphthylester, nonspecific esterase substrates (1-naphthyl acetate, 1-naphthyl butyrate, 5-bromoindoxyl acetate), or several N-blocked L-aminoacyl- and N-blocked L-peptidyl-naphthylamides bearing L-arginine, L-alanine, L-phenylalanine, L-leucine, or L-proline at the P1 subsite. At operative pH values of 4.8 and 3.8 generated during electrophoresis in a stacking and a resolving gel, respectively, the cercarial proteinase migrates toward the cathode. The separated enzyme produces three bands of proteolysis in a gelatin-containing polyacrylamide gel at the optimal pH of 8.4. The presence of the proteinase in the penetration glands, in the secretory canals, and in the secretion from the glands suggests that the enzyme facilitates penetration, thus enabling the larvae to force their way through tissues of their hosts.

Characterization of an extracellular serine protease ofLeishmania (Leishmania) amazonensis

“…These extracellular proteases have been considered as determinants of pathogenicity (Rhoads & Fetterer, 1997). Serine proteases are among the most studied enzymes and have been identified in extracellular products of helminths, such as Schistosoma mansoni (Salter et al 2000), Trichinella spiralis (Todora & Stoyanov, 2000) and Plagiorchis elegans (Moczon, 1996) and their functions in parasite-host tissue invasion and dissemination were confirmed. The blockage of parasite invasion and dissemination was observed through the use of specific protease inhibitors (Lim et al 1999).…”

Leishmania infantum chagasi: A genome-based approach to identification of excreted/secreted proteins

“…Closely related serine proteases have been identified as secreted virulence factors in L. amazonensis [38], Trypanosoma cruzi [39], Plasmodium spp. [40], Toxoplasma gondii [41] and parasitic helminths [42,43], that can digest host membrane proteins, collagen, fibrinogen, gelatin and other proteins and thereby facilitate host tissue invasion and parasite dissemination [44]. Unlike the L. amazonensis serine protease expressed by promastigotes, our ES1 candidate was expressed and secreted exclusively by the LcJ amastigote stage.…”

A cysteine proteinase in the penetration glands of the cercariae of Cotylurus cornutus (Trematoda, Strigeidae)

“…Like other enzymes of this family, together with those which were found in the penetration glands of the cercariae of diplostomid trematodes D. pseudospathaceum and T. excavata (Moczoń 1994a, b; Moczon 2007), the glandular proteinase from C. cornutus cercariae hydrolyzed gelatin, preferred azocoll over azocasein and azoalbumin, and did not hydrolyze elastin, the latter being a good protein substrate for the elastase-like serine proteinase from the penetration glands of the plagiorchiid Neoglyphe sobolevi cercariae (Moczoń 1997). The response of the enzyme extracted from C. cornutus cercariae to the treatment with a number of activators and inhibitors (Table 1) was typical for cysteine proteinases and resembled the response of the “penetration enzymes” from the cercariae of the diplostomid trematodes mentioned above.…”