Functional similarity of sea urchin and mammalian α-amylases

Abstract

α-Amylase from the digestive tube of sea urchin, Anthocidaris crassispina, was isolated by acetone powder, ammonium sulfate fractionation, starch absorption and ion exchange chromatography with DEAE. The enzymatic properties were compared with those of α-amylase from Strongylocentrotus nudas and porcine pancreatic α-amylase, a representative mammalian α-amylase. The activity was purified about 88 times from the crude extract. Optimum pH of the α-amylase was about 6.9 in 50 mM NaCl and about 5.7 in the absence of NaCl at 30°C. Chloride ions activate amylolytic activity in addition to causing a shift of the optimum pH; the K d was 10.6 mM at 30°C. The action pattern of the α-amylase using amylose as a substrate showed a multiple attack mechanism similar to S. nudas and porcine pancreatic α-amylase. In addition to the above properties, the α-amylase from A. crassispina was activated by several monovalent anions. The qualitative activation spectrum was the same as that of porcine pancreatic α-amylase, chloride ion being the best anion activator for both α-amylases. The specific proteinacious inhibitor for animal α-amylases purified from the kidney bean, Phaseolus vulgaris, strongly inhibited the sea urchin α-amylase. It was suggested that there are close functional and structural similarities around the active site of sea urchin and mammalian α-amylases.