Mao Xiang, Wang Weiwu, Jiang Weihong, Zhao Guo-Ping
Laboratory of Microbial Molecular Physiology, Shanghai Institutes for Biological Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China.
Protein J. 2004 Apr;23(3):197-204. doi: 10.1023/b:jopc.0000026415.96041.27.
Glutaryl-7-amino cephalosporanic acid acylase is a member of the N-terminal nucleophilic hydrolase family of enzymes. The crystal structure of the acylase reveals there is a Ser-His-Glu motif composed of Ser1beta, His23beta, and Glu455beta near the active site. This mimics the catalytic triad of Ser-His-Asp in serine proteases. Experiments prove that maturation of this enzyme involves autoproteolysis. It has been shown that Ser1beta is the catalytic residue for the autoproteolysis and catalytic reaction. Our works on site-directed mutagenesis followed by the characterization of mutant enzymes demonstrated that His23beta is essential for autoproteolysis whereas Glu455beta is responsible for the efficiency of the process. Neither His23beta nor Glu455beta is essential for the acylase activity, although they affect the catalytic efficiency.
戊二酰-7-氨基头孢烷酸酰化酶是N端亲核水解酶家族的成员之一。该酰化酶的晶体结构显示，在活性位点附近存在一个由Ser1β、His23β和Glu455β组成的Ser-His-Glu基序。这模拟了丝氨酸蛋白酶中Ser-His-Asp的催化三联体。实验证明，该酶的成熟涉及自蛋白酶解。已表明Ser1β是自蛋白酶解和催化反应的催化残基。我们进行的定点诱变及随后对突变酶的表征工作表明，His23β对自蛋白酶解至关重要，而Glu455β则决定了该过程的效率。His23β和Glu455β对酰化酶活性都不是必需的，尽管它们会影响催化效率。
