Alpha-amylase inhibitor of amadumbe (Colocasia esculenta): Isolation, purification and selectivity toward - amylases from various sources

Two proteins (A-1 and B-2) with -amylase inhibitor activity were extracted and partially purified from Colocasia esculenta tubers through 80% ammonium sulphate fractionation, ion-exchange chromatography on DEAE -Sephacel and gel-chromatography on Sephadex G-100. The molecular weight of A-1 and B-2 were estimated to be about 17000 and 19000 daltons, respectively. The inhibitors inactivated -amylases of animal origin, but had no effect on fungal amylase. Inhibitor A-1 also exhibited activity towards plant amylases, while inhibitor B-2 has no activity on plant amylases. Inhibitor A-1 was the most active against human salivary amylase at pH 6. Inhibitor A-1 was completely destroyed at temperatures above 50°C; while inhibitor B-2 was stable up to 70°C.