Orikoshi Hideyuki, Nakayama Shigenari, Miyamoto Katsushiro, Hanato Chiaki, Yasuda Masahide, Inamori Yoshihiko, Tsujibo Hiroshi
Department of Microbiology, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan.
Appl Environ Microbiol. 2005 Apr;71(4):1811-5. doi: 10.1128/AEM.71.4.1811-1815.2005.
Alteromonas sp. strain O-7 secretes four chitinases (ChiA, ChiB, ChiC, and ChiD) in the presence of chitin. To elucidate why the strain produces multiple chitinases, we studied the expression levels of the four genes and proteins, their enzymatic properties, and their synergistic effects on chitin degradation. Among the four chitinases, ChiA was produced in the largest quantities, followed by ChiD, and the production of ChiB and ChiC changed at lower levels than those of ChiA and ChiD. The expression of the chiA, chiB, chiC, and chiD genes was investigated at the transcriptional level. The RNA transcript of chiA was most strongly induced in the presence of chitin, the expression of chiD followed, and the RNA transcripts of chiB and chiC changed at low levels. The hydrolyzing activities of the four chitinases against various substrates were examined. ChiA was the most active enzyme against powdered chitin, whereas ChiC was the most active against soluble chitin among the four chitinases. ChiD had activities closer to those of ChiA than to those of ChiB and ChiC. ChiB showed no distinctive feature against the chitinous substrates tested. When powdered chitin was treated with the proper combination of four chitinases, an approximately 2.0-fold increase in the hydrolytic activity was observed. These results, together with the results described above, indicate that ChiA plays a central role in chitin degradation for this strain.
嗜 Alteromonas 菌属 O-7 菌株在几丁质存在的情况下会分泌四种几丁质酶（ChiA、ChiB、ChiC 和 ChiD）。为了阐明该菌株为何产生多种几丁质酶，我们研究了这四个基因和蛋白质的表达水平、它们的酶学性质以及它们对几丁质降解的协同作用。在这四种几丁质酶中，ChiA 的产量最高，其次是 ChiD，而 ChiB 和 ChiC 的产量变化幅度低于 ChiA 和 ChiD。我们在转录水平上研究了 chiA、chiB、chiC 和 chiD 基因的表达。chiA 的 RNA 转录本在几丁质存在的情况下诱导最为强烈，其次是 chiD 的表达，而 chiB 和 chiC 的 RNA 转录本变化幅度较小。我们检测了这四种几丁质酶对各种底物的水解活性。在这四种几丁质酶中，ChiA 对粉末状几丁质的活性最高，而 ChiC 对可溶性几丁质的活性最高。ChiD 的活性更接近 ChiA，而不是 ChiB 和 ChiC。ChiB 对所测试的几丁质底物没有明显特性。当用四种几丁质酶的适当组合处理粉末状几丁质时，观察到水解活性提高了约 2.0 倍。这些结果与上述结果一起表明，ChiA 在该菌株的几丁质降解中起核心作用。
