Purification and characterization of α-amylase in Moroccan locust, Dociostaurus maroccanus Thunberg (Orthoptera: Acrididae) and its inhibition by inhibitors from Phaseolus vulgaris L.

Abstract

An α-amylase with molecular weight of 73 kDa was purified from midgut of Dociostaurus maroccanus using ammonium sulfate precipitation, gel filtration, and ion exchange chromatography. The optimal pH and temperature were 6 and 45 °C, respectively. As calculated using Lineweaver–Burk plots, the Km was about 0.62 mM and the Vmax was 1.113 (μmol/min/mg protein). Mn2+, Hg+, Zn2+ and ethylene diamine tetraacetic acid (EDTA) decreased α-amylase activity of D. maroccanus, whereas the addition of K+, Na+, Fe2+, Ba+, Mg2+, Ca2+ and Co2+ increased enzyme activity. Alpha-amylase inhibitors (AI1, AI2) with molecular weights of 43 kDa and 29 kDa, respectively, were purified from the seeds of Phaseolus vulgaris and its inhibitory effect on purified α-amylase of D. maroccanus was investigated. These inhibitors inhibited the D. maroccanus gut α-amylase activity significantly.