Alkaline serine proteases from Helicoverpa armigera: potential candidates for industrial applications

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.