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We previously found a novel chymotrypsin-like protease in honeybee, designated as HCLPase. The recombinant enzyme expressed in insect cells was produced and compared to that in Escherichia coli. Both enzymes showed equivalent molecular size and specificity. However, HCLPase produced in insect cells showed higher specific activity. The C-terminal cleavage sites of HCLPase were phenylalanine, leucine, and tyrosine residues.

We characterized trypsin- and chymotrypsin-like serine alkaline proteases from cotton bollworm, Helicoverpa armigera, for their probable potential application as additives in various bio-formulations. Purification was achieved by using hydroxylapatite, DEAE sephadex and CM sephadex columns, which resulted in increased enzyme activity by 13.76- and 14.05-fold for trypsin and chymotrypsin, respectively. Michaelis-Menten constants (K m ) for substrates of trypsin and chymotrypsin, BApNA and SAAPFpNA, were found to be 1.25 and 0.085 mM, correspondingly. Fluorescent zymogram analysis indicated the presence of five trypsin bands with molecular masses of ∼21, 25, 38, 40, and 66 kDa and two chymotrypsin bands with molecular masses of ∼29 and 34 kDa in SDS-PAGE. The optimum pH was 10.0 and optimum temperature was 50°C for proteolytic activity for the purified proteases. The proteases were inhibited by synthetic inhibitors such as PMSF, aprotonin, leupeptin, pefabloc, and antipain. TLCK and TPCK inhibited about 94 and 90% of trypsin and chymotrypsin activity, respectively, while EDTA, EGTA, E64, pepstatin, idoacetamide, and bestatin did not affect the enzymes. The purified enzymes exhibited high stability and compatibility with metal ions; oxidizing, reducing, and bleaching agents; organic solvents; and commercial detergents. Short life cycles, voracious feeding behavior, and production of multiple forms of proteases in the midgut with rapid catalytic activity and chemostability can serve H. armigera as an excellent alternative source of industrially important proteases for use as additives in stain removers, detergents, and other bio-formulations. Identification of enzymes with essential industrial properties from insect species could be a bioresource., (© 2016 Wiley Periodicals, Inc.)

Two cDNA sequences encoding a trypsin-like and a chymotrypsin-like serine protease (MsT and MsCT, GenBank accession Nos. KP730443 and KP730444, respectively) were cloned from midgut of oriental armyworm, Mythimna separata Walker. Multiple alignments revealed that the deduced amino acid sequences of MsT and MsCT contained a serine protease catalytic motif GDSGGPL and catalytic triads (His, Asp, and Ser). Analyses of tissue and developmental expression of MsT and MsCT showed that they were mainly expressed in midguts and could be detected in first to sixth instar larvae, prepupal and pupal stages. Expressions of both MsT and MsCT were downregulated after 24 h of starvation and upregulated by subsequent insect refeeding. MsT expression in response to 20-hydroxyecdysone (20E) was dose dependent and upregulated after 24 h. However, MsCT expression in response to 20E was downregulated compared with controls. MsCT, but not MsT, transcripts were upregulated after 24 h of Cry1Ac protoxin exposure. These results suggested that MsT was most likely involved in food protein digestion and molting in M. separata whereas MsCT was most likely involved in food protein digestion and Bacillus thuringiensis (Bt) protoxin activation. RNA interference indicated that MsT and MsCT expression levels decreased 76.7 and 86.2% after treated with MsT and MsCT dsRNA, respectively. This study showed that M. separata expressed midgut proteases in line with known lepidopteran counterparts and contributed valuable sequence resource information regarding insect proteases., (© 2016 Wiley Periodicals, Inc.)