Purification and characterization of three amylases from viscera of hard clam Meretrix lusoria

Abstract

Three amylases were purified to electrophoretic homogeneity from viscera of hard clam Meretrix lusoria by ammonium sulfate fractionation, Sepharose 6B, DEAE-Sephadex A-50, Sephadex G-200 and PBE 94 chromatographies. The purified amylases had molecular masses of 49.6, 58.7 and 100 kDa and were designated Al-1, Al-2 and All, respectively. Both Al-1 and Al-2 could digest amylose into glucose and maltose, while All could digest amylose and pullulan into glucose. The optimal pH and temperatures for Al-1, Al-2 and All were 7.0, 7.5 and 7.5, and 40, 50 and 50°C, respectively. According to the substrate specificity, the purified Al-1 and Al-2 were considered to be multifunctional exo- and endo-types of α-amylase-like enzymes, while All was exo-type γ-amylase-like enzyme. They were Ca2+-independent enzymes.