Submitted to: Biochemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/15/2005
Publication Date: 4/30/2005
Citation: Tsybina, T.A., Dunaevsky, Y.E., Belozersky, M.A., Zhuzhikov, D.P., Oppert, B.S., Elpidina, E.N. 2005. A cationic trypsin-like proteinase from the midgut of Tenebrio molitor larvae. Biochemistry (Moscow) 70: 300-305. Interpretive Summary: Little is known about the digestive enzymes of storage insect pests. A digestive enzyme from the yellow mealworm was isolated and characterized. The enzyme was determined to be a serine proteinase, trypsin, and several inhibitors were effective in reducing the activity of this enzyme. This information may be used in the development of novel biopesticides to control coleopteran storage pests.
Technical Abstract: A new trypsin-like proteinase was isolated from the posterior midgut of Tenebrio molitor larvae by ion exchange chromatography and gel filtration. The 25.5 kDa protein was purified to homogeneity as determined by SDS-PAGE and postelectrophoretic activity detection. The pI of 7.4 suggests a cationic protein. With the substrate N'-benzoyl-DL-arginine p-nitroanilide, the pH optimum was 8.5, temperature optimum was 55°C, and Km was 0.04 mM. The proteinase was stable at 25°C for 2 h at pH 5.0 to 9.5. The enzyme was inhibited by phenylmethylsulphonylfluoride and N'-tosyl-L-lysine chloromethyl ketone, demonstrating the trypsin-like property of the enzyme. The enzyme hydrolyzed peptide bonds with arginine and lysine residues in the P1 position, with a preference for arginine, with much less hydrolysis of peptides with proline at positions P2 and P3. Longer peptide substrates were hydrolyzed preferably. The N-terminal amino acid sequence of the enzyme (IVGGSSISISSVPXQIXLQY) has 50-72% identical residues to several insect trypsin-like proteinases.