ORIGINAL ARTICLE

Studies on isolation, purification and inhibition of carboxylesterase from the midgut of fall armyworm (Spodoptera frugiperda)

The fall army worm (FAW) (Spodoptera frugiperda) is a polyphagous pest which causes damage to commercially important cultivated crops such as maize, rice, sorghum, cotton and also different vegetable crops. Carboxyl esterases (CarE, EC.3.1.1.1) or esterases are enzymes in the carboxyl / cholinesterase gene family that catalyze the hydrolysis of carboxyl esters. The carboxylesterases enzyme are the detoxification enzymes in FAW. Therefore, the inhibition of carboxylesterases from FAW would help in pest management. In this scenario, Isolation, purification and inhibition studies were carried out on the midgut carboxylesterase enzyme of FAW. Through a combination of steps including centrifugation, ammonium sulfate gradient precipitation, DEAE-Cellulose ion exchange chromatography, the enzyme was purified from fifth instar larvae of FAW. The final purified carboxylesterase after ion exchange chromatography had a specific activity of 7282.22 units / mg protein, 5.6 – fold of crude homogenate, and a yield of 25%. The purity of esterase was established by PAGE and SDS-PAGE. The SDS-PAGE revealed a molecular weight of approximately 45kDa to 66kDa. Our studies on the purified midgut carboxylesterase showed complete inhibition by organophosphorous inhibitor (10^-4 M). The enzyme was also inhibited by 1x concentration of Lizol (disinfectant) and by different natural extracts (1x) as well.