Kinetics of Hydrolysis Reaction of Chitin Oligomer by a Chitinase Purified from Bacillus subtilis

摘要

Chitinases were extracted and purified from Bacillus subtilis, a bacterium generated from natto, which is a traditional Japanese food. First of all, the best culture condition, culture medium and culture time were decided. Secondly, the crude extracelluler enzyme was obtained by filtration and purified by ion exchange chromatography. As the result, three major fractions with high chitinase activity were obtained and those were named as Chi-1～3. The molecular weights of Chi-1～3 were 85, 30 and 55 kDa, respectively. The optimum pH and the optimum temperature of Chi-1～3 were obtained. For Chi-1～3, the maximum reaction rate and the Michaelis constant were obtained for the hydrolysis of glycol chitin. Chi-3 was found to hydrolyze N-acetyl-chito-oligosaccharides (GlcNAc)_n as follows; (GlcNAc)_5 → (GlcNAc)_3 ＋ (GlcNAc)_2, and (GlcNAc)_4→ 2(GlcNAc)_2.