中文摘要：

[目的]细菌的sah H基因编码S-腺苷同型半胱氨酸水解酶（Sah H）,该酶参与细菌的甲硫氨酸循环（AMC）,调控细菌的多种生理功能。[方法]通过构建重组表达质粒p ET28a-Bru-sah H和p ET28a-Pse-sah H,分别表达布鲁菌（Brucella abortus）S2308株和铜绿假单胞菌（Pseudomonas aeruginosa）PAO1株的Sah H重组蛋白Bru-Sah H和Pse-Sah H。将纯化后的Bru-Sah H、Pse-Sah H以及我们前期表达纯化的禽致病性大肠杆菌（avian pathogenic Escherichia coli,APEC）的Pfs和Lux S蛋白,分别在体外催化S-腺苷同型半胱氨酸（SAH）,通过对产物同型半胱氨酸（HCY）的浓度测定,评价不同重组蛋白的催化活性,并对催化底物时产生的自诱导分子2（AI-2）活性进行检测。[结果]Bru-Sah H和Pse-Sah H分别催化1 mmol·L^-1SAH生成38和47μmol·L^-1HCY,而APEC的Pfs和Lux S蛋白能催化相同浓度的SAH产生401μmol·L^-1HCY。运用哈维弧菌BB170检测上述底物的AI-2活性,结果表明只有同时采用AEPC的Pfs和Lux S蛋白催化SAH,才能形成有活性的AI-2分子,而Bru-Sah H和Pce-Sah H均不能催化SAH形成活性AI-2分子。[结论]Bru-Sah H能催化SAH生成HCY,为进一步研究sah H在布鲁菌感染过程中的作用提供依据。

英文摘要：

[Objectives] The S-adenosylhomocysteine hydrolase （ SahH ） is encoded by sahH gene in Brucella abortus. SahH is a key enzyme in activated methionine cycle （AMC）, which plays an important role in regulation of bacterial physiological functions. [ Methods] In this study, the four recombinant proteins Bru-SahH （ from B. abortus ）, Pse-SahH （ from Pseudomonas aeruginosa）, APEC-LuxS and APEC-Pfs （ from avian pathogenic Escherichia coli） were purified respectively. The catalytic activity of the four recombinant proteins were evaluated by catalyzing substrate S-adenosylhomocysteine（SAH） to produce homocysteine（HCY） in vitro. [ Results ] The results showed that Bru-SahH or Pse-SahH could catalyze SAH （ 1 mmol·L^-1 ） to produce 38 p, mol·L^-1 or 47 mol·L^-1 HCY,respectively,while APEC-LuxS and APEC-Pfs are 401 μmol·L^-1. Furthermore, for confirming whether recombinant proteins could catalyze SAH to produce AI-2 or not,the detection of AI-2 bioassay by Vibrio harveyi strain BB170 was performed. The results demonstrated that APEC-LuxS and APEC-Pfs could catalyze SAH to produce AI-2, while Bru-SahH or Pse-SahH could not. [ Conclusions ] These findings will benefit for future studies on SahH regulation in Brucella abortus.