PURIFICATION AND PROPERTIES OF MYCODEXTRANASE FROM STREPTOMYCES SP J-13-3

An enzyme hydrolyzing nigeran (alternating alpha-1.3-and alpha-1,4-linked glucan) was purified from the culture filtrate of Streptomyces sp. J-13-3, which lysed the cell wall of Aspergillus niger, by precipitation with ammonium sulfate and column chromatographies on DEAE-Sephadex A-50, CM-Sephadex C-50, chromatofocusing, and Sephadex G-100. The final preparation was homogenous in polyacrylamide gel electrophoresis (PAGE). The molecular weight of the enzyme was 68,000 by SDS-PAGE and gel filtration. The optimum pH and temperature for the enzyme activity were 6.0 and 50-degrees-C, respectively. The enzyme was stable in the pH range from 6.0 to 8.0 and up to 50-degrees-C. The enzyme activity was inhibited significantly by Hg+, Hg2+, and p-chloromercuribenzoic acid. The K(m), (mg/ml) for nigeran was 3.33. The enzyme specifically hydrolyzed nigeran into nigerose and nigeran tetrasaccharide by an endo-type of action, indicating it to be a mycodextranase (EC 3.2.1.61) that splits only the alpha-1,4-glucosidic linkages in nigeran.