Biological effects of canatoxin in different insect models: evidence for a proteolytic activation of the toxin by insect cathepsinlike enzymes

• Published in: Journal of economic entomology Vol. 90; no. 2; p. 340
• Main Authors: Carlini, C.R. (Universidade Federal do Rio de Janeiro, Brazil.), Oliveira, A.E.A, Azambuja, P, Xavier-Filho, J, Wells, M.A
• Format: Journal Article
• Language: English
• Published: England 01.04.1997
• Subjects: ADULT EMERGENCE; Aedes; AEDES AEGYPTI; Animals; BIOLOGICAL DEVELOPMENT; Biotransformation; CALLOSOBRUCHUS MACULATUS; CANAVALIA ENSIFORMIS; Cathepsins - metabolism; Coleoptera; CONTROL DE INSECTOS; CRECIMIENTO; CROISSANCE; DESARROLLO BIOLOGICO; DEVELOPPEMENT BIOLOGIQUE; DIET; DIETA; DIGESTION; DROSOPHILA MELANOGASTER; Endopeptidases - metabolism; GROWTH; INSECT CONTROL; Insecta; INSECTICIDAL ACTION; INSECTICIDAS; INSECTICIDE; INSECTICIDES; LARVAE; LARVAS; LARVE; Lectins; LUTTE ANTIINSECTE; Manduca; MANDUCA SEXTA; MOULTING; MUDA; MUE; Orthoptera; PEPTIDASAS; PEPTIDASE; PEPTIDASES; Plant Proteins; Plants; PROTEINAS; PROTEINE; PROTEINS; PROTEOLISIS; PROTEOLYSE; PROTEOLYSIS; REGIME ALIMENTAIRE; Rhodnius; RHODNIUS PROLIXUS; SCHISTOCERCA AMERICANA; SUPERVIVENCIA; SURVIE; SURVIVAL; SYNTHETIC DIETS; TOXICIDAD; TOXICITE; TOXICITY; TOXIN ACTIVATION; TOXINAS; TOXINE; TOXINS; Toxins, Biological
• ISSN: 0022-0493; 1938-291X
• DOI: 10.1093/jee/90.2.340

Canatoxin is a toxic protein isolated from the jackbean, Canavalia ensiformis. The toxin injected intraperitoneally is lethal for mice and rats; however, it is inactive if given orally. In this study, Manduca sexta (L.) (Lepidoptera), Schistocerca americana (Drury) (Orthoptera), Drosophila melanogaster (L.) (Diptera), Aedes aegypti (L.) (Diptera) Rhodnius prolixus (Stal) (Hemiptera), and Callosobruchus maculatus (F.) (Coleoptera) were fed on canatoxin-containing diets. No effects were seen in M. sexta, S. americana, D. melanogaster; or A. aegypti. No traces of canatoxin were found in their feces, suggesting that the protein was digested completely by these insects, which characteristically have a trypsin-based digestion. In contrast, canatoxin was lethal for insects displaying cathepsin-based digestion. Thus, for C. maculatus, a diet containing 0.25% wt:wt canatoxin caused complete inhibition of larval growth. When R. prolixus were fed on canatoxin, 2 effects were seen: impairment of water excretion and increased lethality 48-96 h after feeding. The lethal effect of canatoxin in R. prolixus was blocked partially or completely when the digestion of the toxin by R. prolixus midgut enzymes was impaired. The data showed that canatoxin is highly toxic when ingested by some species of insects but not affecting others, probably in correlation with the characteristics of the digestive process of the insect