Watanabe T, Oyanagi W, Suzuki K, Tanaka H
Department of Biosystem Science, Graduate School of Science and Technology, Niigata University, Japan.
J Bacteriol. 1990 Jul;172(7):4017-22. doi: 10.1128/jb.172.7.4017-4022.1990.
Bacillus circulans WL-12, isolated as a yeast cell wall-lytic bacterium, secretes a variety of polysaccharide-degrading enzymes into culture medium. When chitinases of the bacterium were induced with chitin, six distinct chitinase molecules were detected in the culture supernatant. These chitinases (A1, A2, B1, B2, C, and D) showed the following distinct sizes and isoelectric points: Mr 74,000, pI 4.7 (A1); Mr 69,000, pI 4.5 (A2); Mr 38,000, pI 6.6 (B1); Mr 38,000, pI 5.9 (B2); Mr 39,000, pI 8.5 (C); and Mr 52,000, pI 5.2 (D). Among these chitinases, A1 and A2 had the highest colloidal-chitin-hydrolyzing activities. Chitinase A1 showed a strong affinity to insoluble substrate chitin. Purified chitinase A1 released predominantly chitobiose [(GlcNAc)2] and a trace amount of N-acetylglucosamine (GlcNAc) from colloidal chitin. N-terminal amino acid sequence analysis of chitinases A1 and A2 indicated that chitinase A2 was generated from chitinase A1, presumably by proteolytic removal of a C-terminal portion of chitinase A1. Since chitinase A2 did not have the ability to bind to chitin, the importance of the C-terminal region of chitinase A1 to the strong affinity of chitinase A1 to substrate chitin was suggested. Strong affinity of the chitinase seemed to be required for complete degradation of insoluble substrate chitin. From these results, it was concluded that chitinase A1 is the key enzyme in the chitinase system of this bacterium.
环状芽孢杆菌WL - 12作为一种酵母细胞壁裂解细菌被分离出来，它能向培养基中分泌多种多糖降解酶。当用几丁质诱导该细菌的几丁质酶时，在培养上清液中检测到六种不同的几丁质酶分子。这些几丁质酶（A1、A2、B1、B2、C和D）具有以下不同的大小和等电点：分子量74,000，等电点4.7（A1）；分子量69,000，等电点4.5（A2）；分子量38,000，等电点6.6（B1）；分子量38,000，等电点5.9（B2）；分子量39,000，等电点8.5（C）；分子量52,000，等电点5.2（D）。在这些几丁质酶中，A1和A2具有最高的胶体几丁质水解活性。几丁质酶A1对不溶性底物几丁质表现出很强的亲和力。纯化的几丁质酶A1主要从胶体几丁质中释放出壳二糖[（GlcNAc）2]和微量的N - 乙酰葡糖胺（GlcNAc）。几丁质酶A1和A2的N端氨基酸序列分析表明，几丁质酶A2可能是由几丁质酶A1通过蛋白水解去除几丁质酶A1的C端部分而产生的。由于几丁质酶A2没有结合几丁质的能力，这表明几丁质酶A1的C端区域对几丁质酶A1与底物几丁质的强亲和力很重要。几丁质酶的强亲和力似乎是完全降解不溶性底物几丁质所必需的。从这些结果可以得出结论，几丁质酶A1是该细菌几丁质酶系统中的关键酶。
