Properties and catalytic mechanism of γ-glutamyltranspeptidase from B.subtilis NX-2  

作　　者：Qian WANG Zhong YAO Zhijing XUN Xiaoying XU Hong XU Ping WEI 

机构地区：[1]College of Life Science and Pharmacy,Nanjing University of Technology,Nanjing 210009,China

出　　处：《Frontiers of Chemical Science and Engineering》2008年第4期456-461,共6页化学科学与工程前沿（英文版）

摘　　要：Sinceγ-glutamyltranspeptidase(GGT)especially catalyses the transfer of theγ-glutamyl moiety to a variety of amino acids and short peptides,GGT has important practical value for enzymatic synthesis ofγ-glutamyl compounds.In this paper,the GGT produced from Bacillus subtilis NX-2 was purified by a combination of ammonium sulfate fractionation and ion exchange chromatography,and the properties of purified GGT were investigated.At the conditions of pH 10.0,D-glutamine(D-Gln)/L-tryptophan(L-Trp)with a molar ratio of 5:7,a temperature 40℃ and a reaction time of 4 h,a higher conversion rate of 42%was obtained.According to the time course,the catalytic mechanism of enzymatic synthesis ofγ-D-glutamyl-L-tryptophan(γ-D-Gln-L-Trp)was discussed.It was demonstrated that the GGT can catalyze not only the reaction of transpeptidation,but also the irreversible hydrolysis of the products which results in the decrease of the yield of the products.The affinity parameter of GGT to D-Gln(Km)was 5.08 mmol·L-1 and the maximum reaction rate of transpeptidation(rmax)was determined as 0.034 mmol·min-1·L-1,while the affinity parameter of GGT toγ-D-Gln-L-Trp(K’m)was 2.267 mmol·L-1,and the maximum reaction rate of hydrolysis(r’max)was 0.012 mmol·min-1·L-1.

关 键 词：c-glutamyltranspeptidase purification prop-erties c-D-glutamyl-L-Tryptophan catalytic mechanism 

分 类 号：O62[理学—有机化学]