Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/28/2009
Publication Date: 6/30/2009
Publication URL: http://hdl.handle.net/10113/28658
Citation: Vinokurov, K.S., Elpidina, E.N., Zhuzhikiv, D.P., Oppert, B.S., Kodrik, D., Sehnal, F. 2009. Digestive proteolysis organization in two closely related Tenebrionid beetles: Red flour beetle (Tribolium castaneum) and confused flour beetle (Tribolium confusum). Archives of Insect Biochemistry and Physiology. 70(4): 254-279. Doi: http://dx.doi.org/10.1002/arch.20299. Interpretive Summary: Little is known about the specifics of food digestion in Tribolium spp. beetles. We provide a detailed and thorough characterization of protein digestion in the red and confused flour beetles, two important pests of stored-products. Proteins in food are digested primarily by a specific class of enzymes called cysteine peptidases, with a minor contribution by serine peptidases. Understanding the complex system of digestion in flour beetles will improve their control using digestive inhibitors or microbial toxins.
Technical Abstract: The spectra of Tribolium castaneum and T. confusum larval digestive peptidases were characterized with respect to the spatial organization of protein digestion in the midgut. The pH of midgut contents in both species increased from 5.6-6.0 in the anterior to 7.0-7.5 in the posterior midgut. However, the pH optimum of the total proteolytic activity of the gut extract from either insect was pH 4.1. Approximately 80% of the total proteolytic activity was in the anterior and 20% in the posterior midgut of either insect when evaluated in buffers simulating the pH and reducing conditions characteristic for each midgut section. The general peptidase activity of gut extracts from either insect in pH 5.6 buffer was mostly due to cysteine peptidases. In the weakly alkaline conditions of the posterior midgut, the serine peptidase contribution was 31 and 41% in T. castaneum and T. confusum, respectively. A postelectrophoretic peptidase activity assay with gelatin also revealed the important contribution of cysteine peptidases in protein digestion in both Tribolium species. The use of a postelectrophoretic activity assay with p-nitroanilide substrates and specific inhibitors revealed a set of cysteine and serine endopeptidases, 8 and 10 for T. castaneum, and 7 and 9 for T. confusum, respectively. Serine peptidases included trypsin-, chymotrypsin- and elastase-like enzymes, the latter being for the first time reported in Tenebrionid insects. These data support a complex system of protein digestion in the Tribolium midgut with the fundamental role of cysteine peptidases.