Distribution of proteinases and carbohydrases in the midgut of larvae of the sweetpotato weevil Cylas formicarius elegantulus and response of proteinases to inhibitors from sweet potato

Abstract

Endoproteinase activity was confined to luminal fluid from anterior and posterior ventricular regions of midguts of larvae of the sweetpotato weevil, Cylas formicarius elegantulus (Summers). Aminopeptidase was found in luminal fluid (18%) but was primarily associated with insoluble fractions from cells of the posterior ventriculus (82%). Depending on substrate, carboxypeptidase activity was about equally distributed between luminal fluid and insoluble fractions from posterior ventriculus cells. Amylase was found in luminal fluid in both the anterior and posterior ventriculus. Five bands of amylase activity were detected on starch zymograms following electrophoresis of whole midgut samples. Three of the amylase bands may be plant‐derived. At least two α‐glucosidases were present, one secreted and one bound to anterior ventriculus cells. β‐Glucosi‐dase activity was bound to anterior ventriculus cells whereas α‐galactosidase activity was confined to luminal fluid. β‐Galactosidase and cellulase activities were found in both luminal fluid and the insoluble cell fraction. Thus, initial digestion of large protein and carbohydrate polymers occurs in luminal fluid in both anterior and posterior ventriculus regions. However, terminal digestion of oligopeptides occurs primarily in the posterior ventriculus while terminal digestion of oligosaccharides occurs in the anterior ventriculus. A 20‐fold difference in trypsin‐inhibitor concentration was found among five sweetpotato cultivars. Endoproteinases from sweetpotato weevil larvae were inhibited by extracts from the cultivars but cultivars with relatively high concentrations of inhibitor were previously shown to be susceptible to weevil attack in field trials. RÉSUMÉ Distribution des protéinases et des carbohydrases dans l'intestin moyen des larves de Cylas formicarius elegantulus et réponse des protéinases aux inhibiteurs d'Ipomoea batatas L'activité endoprotéinase était limitée au liquide de la lumière des régions ventriculaires antérieure et postérieure de l'intestin moyen des larves de Cylas formicarius elegantulus Summers. Les aminopeptidases ont été trouvées dans le liquide de la lumière (18%), mais étaient principalement associées avec les fractions insolubles des cellules du ventricule postérieur (82%). Suivant le substrat, l'activité carboxypeptidase était à peu près également répartie entre le liquide de la lumière et les fractions insolubles des cellules du ventricule postérieur. L'amylase, enzyme secrétée, a été observée à la fois dans la lumière antérieure et postérieure. Cinq bandes d'activité amylase ont été révélées sur zymogrammes d'amidon après électrophorèse d'intestins moyens entiers. Trois des bandes d'amylase pouvaient provenir de la plante. Il y avait au moins 2 α‐glucosidases, une secrétée et une liée aux cellules du ventricule antérieur. L'activité β‐glucosidase était liée aux cellules du ventricule antérieur, tandis que l'activité α‐galactosidase était limitée au fluide de la lumière. Les activités β‐galaetosidase et cellulase ont été trouv...

Sequencing and characterization of the citrus weevil, Diaprepes abbreviatus, trypsin cDNA

“…2) indicating that the pH of D. abbreviatus gut is probably alkaline as shown for Lepidoptera and mosquitoes. Trypsin‐like activity has been detected previously in several weevils, such as the rice weevil ( S. oryzae ), granarius granary weevil ( S. oryzea Summers ), and sweet potato weevil ( Cylas formicarius elegantus ) [13,41,42]. The major proteinase of the boll weevil ( Anthonomus grandis ) was found to be a trypsin‐like enzyme, with maximal midgut activity at pH 10–11 [14].…”

Amylase/proteinase ratios in larval midguts of ten stored‐product insects

“…Adults of S. oryzae also have an extremely active amylase with levels 3-fold and 8-fold higher than that found in adults of S. granarius or S. zeamais Motschulsky, respectively (Baker & Woo, 1984). Larvae of the four granivorous beetles, S. oryzae, S. granarius, T. molitor, and T. castaneum had much higher amylase levels individually and as a group than the other species.…”

“…Highest amylase activities based on fresh weight and midgut protein were found in larvae of S. oryzae. Adults of S. oryzae also have an extremely active amylase with levels 3-fold and 8-fold higher than that found in adults of S. granarius or S. zeamais Motschulsky, respectively (Baker & Woo, 1984). Amylase was barely detectable in A.…”

“…Quantitative comparisons of specific activities and ratios of midgut enzymes among ten of these species were therefore conducted. Although enzymes associated with terminal stages of digestion of oligopeptides and oligosaccharides in phytophagous species are bound to specific regions of the midgut, enzymes associated with initial hydrolysis of large protein and carbohydrate polymers are soluble and are found in lumen contents (Terra et al, 1979;Ferreira & Terra, 1982;Baker et al, 1984). Since ratios and activities of these latter enzymes are most likely to reflect the degree of adaptation to food or diet components, midgut levels of amylase, general proteinase activity, trypsin, and soluble aminopeptidase in larvae of these species were determined.…”

Isolation and Characterization of a Phaseolus vulgaris Trypsin Inhibitor with Antiproliferative Activity on Leukemia and Lymphoma Cells

“…Leguminous seeds are a rich source of proteins, including protease inhibitors, lectins [ 14 ], antifungal proteins [ 15 ], ribosome inactivating proteins [ 16 ], and arcelins [ 17 ]. Some of the proteins have interesting biological activities, such as insecticidal [ 14 ], immunomodulatory [ 5 ], antifungal [ 18 ], and antitumor [ 8 , 10 ] activities. The intent of the present study was to isolate a trypsin inhibitor from the gold bean and to test it for inhibitory action on tumor cells, viral enzymes, and fungal growth.…”