PREPARATION AND SOME PROPERTIES OF A NOVEL MALTOPENTAOSE-FORMING ENZYME OF A PSEUDOMONAS SPECIES

A novel enzyme, of a Pseudomonas species, was purified by ammonium sulfate fractionation and column chromatographies on DEAE-Toyopearl 650M and Toyopearl HW-55s. The activity recovery was 87% at the ammonium sulfate fractionation step and 44% at the final step of the purification, respectively. The purified enzyme was homogeneous electrophoretically and its molecular weight was 72,000. The optimum pH and temperature were 6.5 and 55°C, respectively. The enzyme was stable up to 45°C in the pH range of 6.5 to 9.0 for 1 hr, and thermostable in the presence of 2mM CaCl2 up to 50°C. The isoelectric point of the enzyme was 6.5. The enzyme activity was inhibited by metal ions such as Zn2+, Cu2+, Ag+ and Hg2+, and enhanced by Rb+, Mg2+, Co2+ and Ca2+. The enzyme specifically produced maltopentaose from starch in the initial stage of the reaction, finally producing maltose and maltotriose. The enzyme did not act on glucose, maltose or maltotriose, and maltohexaose was considerably resistant to the enzyme’s action. In the initial stage of hydrolysis, G2 and G5 were formed from G7, and thus G3+G5 from G8, G4 + G5 from G9, G5 + G5 from G10, and G6 +G5 from G11. Through the next action, G4 and G5 were degraded to G2+G2 and G2+G3, respectively. The enzyme action proceeds over the branching points of amylopectin to produce large amounts of G2 and G3, and a residual amount of oligosaccharides having less than 10 glucose units in the final stage of the reaction. © 1990 by the Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.