Kawase Tomokazu, Yokokawa Shinya, Saito Akihiro, Fujii Takeshi, Nikaidou Naoki, Miyashita Kiyotaka, Watanabe Takeshi
Department of Applied Biological Chemistry, Faculty of Agriculture, Niigata University, Ikarashi, Niigata, Japan.
Biosci Biotechnol Biochem. 2006 Apr;70(4):988-98. doi: 10.1271/bbb.70.988.
Streptomyces coelicolor A3(2) has 13 chitinase genes encoding 11 family 18 and two family 19 chitinases. To compare enzymatic properties of family 19 chitinase and family 18 chitinases produced by the same organism, the four chitinases (Chi18bA, Chi18aC, Chi18aD, and Chi19F), whose genes are expressed at high levels in the presence of chitin, were produced in Escherichia coli and purified. The effect of pH on the hydrolytic activity was very different not only among the four chitinases but also among the substrates. The hydrolytic activity of Chi19F, family 19 chitinase, against soluble substrates was remarkably high as compared with three family 18 chitinases, but was the lowest against crystalline substrates among the four chitinases. On the contrary, Chi18aC, a family 18-subfamily A chitinase, showed highest activity against crystalline substrates. Only Chi19F exhibited significant antifungal activity. Based on these observations, the roles of family 19 chitinases are discussed.
天蓝色链霉菌A3(2)有13个几丁质酶基因，编码11个18家族和2个19家族的几丁质酶。为了比较同一生物体产生的19家族几丁质酶和18家族几丁质酶的酶学特性，在几丁质存在下基因高水平表达的4种几丁质酶（Chi18bA、Chi18aC、Chi18aD和Chi19F）在大肠杆菌中产生并纯化。pH对水解活性的影响不仅在这4种几丁质酶之间有很大差异，在底物之间也有很大差异。19家族几丁质酶Chi19F对可溶性底物的水解活性与3种18家族几丁质酶相比非常高，但在这4种几丁质酶中对结晶底物的水解活性最低。相反，18家族A亚家族几丁质酶Chi18aC对结晶底物表现出最高活性。只有Chi19F表现出显著的抗真菌活性。基于这些观察结果，对19家族几丁质酶的作用进行了讨论。
