Characterization and inhibition kinetics of gut α-amylase from Chilo partellus through Lineweaver- Burk, fractional velocity and combination plots.

Chilo partellus is a serious pest of agricultural crops. The present investigation was carried out to characterize the gut α-amylase from C. partellus and to explore its inhibition kinetics with various α-amylase inhibitors. α-amylase eluted at ve/vo of 1.38–1.48 on sephadex G-100 column chromatography with 15.58 folds purification. It had a single isoform of 65 KDa with an optimum pH of 8.0. It was thermally stable up to 50 °C and showed the highest activity with starch. A critical analysis of Lineweaver–Burk plot showed that the Michaelis constant, Km, of α-amylase for starch was 0.32 mg/ml while Vmax was observed to be 1.47 nmoles of reducing sugars formed/min/ml of enzyme. Among the various chemicals studied, citric acid, salicylic acid, oxalic acid, zinc chloride and calcium nitrate were found to be the potent inhibitors of α-amylase activity. Through a concerted study of the primary and secondary plots of Lineweaver–Burk, fractional velocity and combination plots, it was revealed that citric acid, salicylic acid, oxalic acid, zinc chloride and calcium nitrate caused complete inhibition of α-amylase activity by mixed- non-competitive-uncompetitive mode. [ABSTRACT FROM AUTHOR]