Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/17/2006
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. Fractionation of digestive proteinases from Tenebrio molitor (Coleoptera: Tenebrionidae) larvae and role in protein digestion. Comparative Biochemistry and Physiology, Part B 145: 138-146. Available: doi: 10.1016/j.cbpb.2006.05.004. Interpretive Summary: Beetles are some of the most serious pests of stored grains and processed commodities. As part of a comprehensive study of digestive enzymes in larvae of the yellow mealworm, a pest of stored products, proteinases were purified using chromatographic techniques and characteristics of purified proteinases were obtained. Specific proteinases were identified that are responsible for the initial stages of digestion of the main dietary protein for mealworm larvae, oat globulin. These proteinases provide potential targets for inhibitors that can be used in an integrated pest management strategy.
Technical Abstract: Tenebrio molitor larval digestive proteinases were purified and characterized by gel filtration chromatography combined with activity electrophoresis. Cysteine proteinases, consisting of at least six distinct activities, were found in three chromatographic peaks in anterior and posterior midgut chromatographies. The major activity in the anterior midgut, peak cys II, consisted of cysteine proteinases with Mm of 23 kDa. The predominant peak in the posterior, cys I, was represented by 38 kDa proteinases. The activity of all cysteine proteinases was maximal in pH 5.0-7.0 and displayed 80% stability in pH 4.0-7.0 buffers. In the conditions of the last third of the midgut, the activity and stability of cysteine proteinases was sharply decreased. Trypsin-like activity included a minor peak of "heavy" trypsins with Mm 59 kDa located mainly in the anterior midgut. An in vitro study of the initial stages of digestion of the main dietary protein, oat 12S globulin, by anterior midgut proteinases revealed that hydrolysis occurred through the formation of intermediate high Mm products, similar to those formed during oat seed germination. Cysteine proteinases from the Cys III peak and heavy trypsins were capable of only limited proteolysis of the protein, while incubation with cys II proteinases resulted in substantial hydrolysis of the globulin.