Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2006
Publication Date: 7/1/2006
Citation: Vinokurov, K.S., Elpidina, E.N., Oppert, B.S., Prabhakar, S., Zhuzhikov, D.P., Dunaevsky, Y.E., Belozersky, M.A. Diversity of digestive proteinases in Tenebrio molitor (Coleoptera: Tenebrionidae) larvae. Comparative Biochemistry and Physiology, Part B 145: 126-137. Available: doi:10.1016/j.cbpb.2006.05.005. Interpretive Summary: Yellow mealworm larvae have a complex system of digestive proteinases, and, as such, provide a good model to study the interactions of plant proteinase inhibitors and pests. Therefore, the complete spectrum of digestive proteinases used by yellow mealworm larvae for food digestion was characterized. Proteinases were found in compartments of the gut that were conducive to maximal activity. Multiple forms of cysteine- and serine-type proteinases were found. This information will be used to study pest interactions with cereal inhibitors and ultimately to design new biopesticides for stored-product pest management.
Technical Abstract: The spectrum of Tenebrio molitor larvae digestive proteinases was studied in the context of spatial organization of protein digestion in the midgut. The pH of midgut contents increased from 5.2–5.6 to 7.8–8.2 from the anterior to the posterior. This pH gradient was reflected in the pH optima of the total proteolytic activity, 5.2 in the anterior and 9.0 in the posterior midgut. Of the total proteolytic activity in the midgut, 64% was in the anterior and 36% in the posterior. In the anterior midgut, two-thirds of the total activity was due to cysteine proteinases, while the remainder was from serine proteinases. However, in the posterior midgut, 76% of the proteolytic activity was from serine proteinases. Cysteine proteinases from the anterior midgut were represented by a group of anionic fractions with similar electrophoretic mobility. Trypsin-like activity, predominant in the posterior midgut, was due to three anionic and one cationic proteinases. Chymotrypsin-like proteinases, also predominant in the posterior, were represented by four anionic and one cationic proteinase, four with an extended binding site. Latent proteinase activity also was detected. These data support a complex system of protein digestion, and the correlation of proteinase activity and pH indicates a physiological mechanism of enzyme regulation in the gut.