A Pseudomonas intracellular amylase with high activity on maltodextrins and cyclodextrins

An intracellular amylase from Pseudomonas MSl was purified 95-fold in a 14% yield by fractionation with (NH4) 2SO4, followed by chromatographies on CM-cellulose, hydroxylapatite and Sephadex G-200. On polyacrylamide gel electrophoresis at pH 8.3 it gave a single band and its molecular weight was determined to be 96 000 from its mobility on sodium dodecylsulfate gel electrophoresis. Its activity was maximal at pH 5.5 and 50 degrees C. This enzyme hydrolyzed maltotriose and maltotetraose faster than amylose, but did not hydrolyze maltose. It also rapidly hydrolyzed a series of cyclomaltodextrins. Amylopectin and glycogen, which have branched structures, were attacked much slower than amylose. The enzyme cleaved the substrates in an endo-wise fashion and produced almost equimolar amounts of glucose and maltose as the final products from various substrates. The enzyme mechanism is discussed on the basis of quantitative autoradiographic data. The K-m values for maltotriose, maltotetraose, cyclomaltohexaose, corn amylose and waxycorn amylopectin were 1.0, 1.4, 3.5, 3.3 and 13 - 10-minus 3 g/ml, respectively. The products of the enzyme had an alpha-configuration. Thus, this enzyme is a specific alpha-amylase.