Kawase Tomokazu, Saito Akihiro, Sato Toshiya, Kanai Ryo, Fujii Takeshi, Nikaidou Naoki, Miyashita Kiyotaka, Watanabe Takeshi
Department of Applied Biological Chemistry, Faculty of Agriculture, Niigata University, Ikarashi-2, Niigata 950-2181, Japan.
Appl Environ Microbiol. 2004 Feb;70(2):1135-44. doi: 10.1128/AEM.70.2.1135-1144.2004.
In organisms other than higher plants, family 19 chitinase was first discovered in Streptomyces griseus HUT6037, and later, the general occurrence of this enzyme in Streptomyces species was demonstrated. In the present study, the distribution of family 19 chitinases in the class Actinobacteria and the phylogenetic relationship of Actinobacteria family 19 chitinases with family 19 chitinases of other organisms were investigated. Forty-nine strains were chosen to cover almost all the suborders of the class Actinobacteria, and chitinase production was examined. Of the 49 strains, 22 formed cleared zones on agar plates containing colloidal chitin and thus appeared to produce chitinases. These 22 chitinase-positive strains were subjected to Southern hybridization analysis by using a labeled DNA fragment corresponding to the catalytic domain of ChiC, and the presence of genes similar to chiC of S. griseus HUT6037 in at least 13 strains was suggested by the results. PCR amplification and sequencing of the DNA fragments corresponding to the major part of the catalytic domains of the family 19 chitinase genes confirmed the presence of family 19 chitinase genes in these 13 strains. The strains possessing family 19 chitinase genes belong to 6 of the 10 suborders in the order Actinomycetales, which account for the greatest part of the Actinobacteria: Phylogenetic analysis suggested that there is a close evolutionary relationship between family 19 chitinases found in Actinobacteria and plant class IV chitinases. The general occurrence of family 19 chitinase genes in Streptomycineae and the high sequence similarity among the genes found in Actinobacteria suggest that the family 19 chitinase gene was first acquired by an ancestor of the Streptomycineae and spread among the Actinobacteria through horizontal gene transfer.
在高等植物以外的生物体中，19 家族几丁质酶最早是在灰色链霉菌 HUT6037 中发现的，后来证明该酶在链霉菌属物种中普遍存在。在本研究中，调查了 19 家族几丁质酶在放线菌纲中的分布以及放线菌 19 家族几丁质酶与其他生物体 19 家族几丁质酶的系统发育关系。选择了 49 个菌株以覆盖放线菌纲几乎所有的亚目，并检测了几丁质酶的产生情况。在这 49 个菌株中，有 22 个在含有胶体几丁质的琼脂平板上形成了透明圈，因此似乎产生了几丁质酶。使用与 ChiC 的催化结构域相对应的标记 DNA 片段对这 22 个几丁质酶阳性菌株进行了 Southern 杂交分析，结果表明至少 13 个菌株中存在与灰色链霉菌 HUT6037 的 chiC 相似的基因。对 19 家族几丁质酶基因催化结构域主要部分对应的 DNA 片段进行 PCR 扩增和测序，证实了这 13 个菌株中存在 19 家族几丁质酶基因。拥有 19 家族几丁质酶基因的菌株属于放线菌目 10 个亚目中的 6 个，放线菌目占放线菌纲的大部分：系统发育分析表明，放线菌中发现的 19 家族几丁质酶与植物 IV 类几丁质酶之间存在密切的进化关系。19 家族几丁质酶基因在链霉菌科中的普遍存在以及放线菌中发现的基因之间的高度序列相似性表明，19 家族几丁质酶基因最初是由链霉菌科的一个祖先获得的，并通过水平基因转移在放线菌中传播。
