Journal
ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY
Volume 70, Issue 4, Pages 254-279Publisher
WILEY
DOI: 10.1002/arch.20299
Keywords
Coleopteran insects; insect digestive peptidases; organization of digestion; Tribolium castaneum; Tribolium confusum
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Funding
- INTAS Post Doctoral Fellowship [06-1000014-6040]
- Russian Foundation for Basic Research [08-04-00737-a, 09-04-01449-a, 09-04-91289-INIS_a]
- Czech Science Foundation [522/06/1591]
- Czech Ministry of Education, Youth, and Sports [1M06030]
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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 for 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 characteristics 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 endopeptidases, 8 and 10 for T.castaneum, and 7 and 9 for T. confusum, repectively. 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. (c) 2009 Wiley Periodicals, Inc.
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