Preparation and some properties of a novel maltotetraose-forming enzyme of Pseudomonas saccharophila.

It was found that Pseudomonas saccharophila produced a maltotetraose-forming enzyme . The enzyme was purified by ammonium sulfate fractionation and column chromatography on DEAE-Toyopearl 650M and Toyopearl HW-55s. The activity recovery was 19% at the final step of the purification . The purified enzyme was homogeneous electrophoretically and its molecular weight was 62, 000. The optimum pH and temperature were 6.7 and 55°C, respectively. The enzyme was stable up to 40°C in the pH range of 5.5 to 10.5 for 1 hr, and thermostable in the presence of 2 mM CaCl2, up to 45°C . The isoelectric point of the enzyme was 4.7. The enzyme activity was inhibited by metalions such as Ag+, Hg2+, Co2+, Cu2+, Fe3+, Al3+, Zn2+, and enhanced by Sr2+. The enzyme specifically produced maltotetraose from starch, did not act on glucose, maltose, maltotriose, and maltotetraose. The enzyme action proceeded from non-reducing ends of the substrates and seemed to be difficult skipping over the branches of amylopectin.