Biochemical characterization of a novel extracellular pullulan 6-glucanohydrolase from Bacillus circulans S-1

Bacillus circulans S-1 extracellular pullulan 6-glucanohydrolase (EP) (EC 3.2.1.41) has been characterized with a purified enzyme of 140 kDa. The N-terminal amino acid sequence of the purified enzyme was P-L-N-M-S-Q-P. The enzyme displayed a temperature optimum of around and a pH optimum of around pH 9.0. The enzyme was stable to incubation from pH 4.0 to pH 11.0 at for 48h. The presence of substrate allowed the protection of the enzyme from heat inactivation. The activity of the enzyme was stimulated by several metal ions such as Mn2+ and Ca2+. The enzyme had an apparent Km of 7.92 mg/ml for pullulan. The purfied enzyme completely hydrolysed pullulan to maltotriose.