Hu Rouh-Mei, Chiang Kai-Hung, Chang Yi-Chih, Yang Tsuey-Ching
Department of Biotechnology and Bioinformatics, Asia University, Taichung 413, Taiwan, ROC.
Department of Medical Laboratory Science and Biotechnology, China Medical University, Taichung 404, Taiwan, ROC.
J Med Microbiol. 2009 Mar;58(Pt 3):318-321. doi: 10.1099/jmm.0.000380-0.
Stenotrophomonas maltophilia KH has two acid beta-lactamases with isoelectric points (pIs) of 4.6 and 5.4, and several basic beta-lactamases (pIs >7.0) that produce a ladder-shaped pattern by IEF. An isogenic L2 mutant, KHL2(xylE), was constructed by gene replacement. From IEF and native PAGE zymograms of strains KH and KHL2(xylE), it was demonstrated that the basic beta-lactamases and the acid beta-lactamase with pI 5.4 are encoded by the same L2 gene and that the active types of these L2 charge variants were dependent on the buffer pH. The beta-lactamase activities of these L2 charge variants in phosphate buffer at pH 7.0 and 8.0 were 1075+/-29 and 1114+/-81 U mg(-1), respectively. These results indicate that L2 charge variants give S. maltophilia a better chance of adapting and surviving in response to changes in the environment.
嗜麦芽窄食单胞菌KH有两种等电点（pIs）分别为4.6和5.4的酸性β-内酰胺酶，以及几种碱性β-内酰胺酶（pIs>7.0），这些碱性β-内酰胺酶通过等电聚焦（IEF）产生梯形图谱。通过基因置换构建了一个同基因的L2突变体KHL2（xylE）。从菌株KH和KHL2（xylE）的IEF和天然聚丙烯酰胺凝胶电泳酶谱图可知，碱性β-内酰胺酶和等电点为5.4的酸性β-内酰胺酶由同一个L2基因编码，并且这些L2电荷变体的活性类型取决于缓冲液的pH值。这些L2电荷变体在pH 7.0和8.0的磷酸盐缓冲液中的β-内酰胺酶活性分别为1075±29和1114±81 U mg（-1）。这些结果表明，L2电荷变体使嗜麦芽窄食单胞菌有更好的机会适应环境变化并生存下来。
