PURIFICATION AND PROPERTIES OF MYCODEXTRANASE FROM BACILLUS-CIRCULANSNHB-1

A Gram-positive bacterium, Bacillus circulans, isolated from soil was found to produce an enzyme hydrolyzing nigeran (mycodextran, alternati ng alpha-1,3- and alpha-1,4-linked glucan). The molecular weight of th e purified enzyme was 120,000 and its isoelectric point was 8.30. The optimum pH and temperature for the enzyme activity were 6.0 and 50 deg rees C, respectively. The enzyme was stable in the pH range from 6.0 t o 7.0 and up to 50 degrees C. The K-m (mg/ml) for nigeran was 1.37. Th e enzyme specifically hydrolyzed the nigeran into nigerose and nigeran tetrasaccharide by an endo-type action, indicating that it is a mycod extranase (EC 3.2.1.61) cleaving only the alpha-1,4-glucosidic linkage s in nigeran. The N-terminal amino acid sequence of the purified enzym e of B. circulans (APTVYEAESAAKTGGV) was different from that of the my codexstranase purified from Streptomyces sp. J-13-3 (XDPGDPTDPDPSGVGAT LPF).