Multiple attack hypothesis of α-amylase action: Action of porcine pancreatic, human salivary, and Aspergillus oryzae α-amylases

Abstract

Three conceptual action patterns of α-amylase hydrolysis of amylose have been considered: single chain, multichain, and multiple attack. To test these concepts, curves were obtained relating the drop in amylose-iodine color to the increase in reducing value for amylolysis by human salivary (HS), porcine pancreatic (PP), Aspergillus oryzae (AO) α-amylases, and 1 m H 2SO 4. The observed differences in the curves for the amylases could only be interpreted as due to differences in degree of multiple attack. To test these concepts further, amylase digests at various stages of hydrolysis were separated by ethanol precipitation into polysaccharide and oligosaccharide fractions. The degree of multiple attack was determined from the ratio of the reducing value of the oligosaccharide fraction to that of the polysaccharide fraction. Under optimal conditions of pH and temperature, PP had a degree of multiple attack of 6, three times that of HS or AO. At pH 4.5, the degree of multiple attack of PP did not change, although its activity was reduced 10-fold. At pH 10.5, however, the degree of multiple attack was reduced to 0.7, approaching a multichain pattern.