ISOLATION OF NIGERAN-DEGRADING ARTHROBACT ER SP NHB-10 AND PROPERTIESOF MYCODEXTRANASE PRODUCED BY THE ISOLATED BACTERIUM - NOTE

A nigeran-degrading bacterium was isolated from soil and identified as Arthrobacter sp. (strain NHB-10). An enzyme hydrolyzing nigeran (alte rnating alpha-1,3- and alpha-1,4-linked glucan) was partially purified from the culture filtrate of strain NHB-10 by chromatographies on DEA E-Sepharose, Sephadex G-100 and DEAE-Sephadex A-50. The enzyme prepara tion showed a single band with a molecular weight of about 70,000 on s odium dodecyl sulfate-polyacrylamide gel electrophoresis, but two band s with different isoelectric points of 7.80 and 7.40 on a thin-layer a garose gel for electrofocusing. The enzyme specifically hydrolyzed the nigeran into nigerose and nigeran tetrasaccharide by an endo-type act ion, indicating that it is a mycodextranase (EC 3.2.1.61) cleaving onl y the alpha-1,4-glucosidic bonds in nigeran. The optimum pH and temper ature for the enzyme activity were 6.0 and 50 degrees C, respectively. The enzyme was stable in the pH range from 6.0 to 9.0 and up to 50 de grees C.