Changing the specificity of α-amino acid ester hydrolase toward para-hydroxyl cephalosporins synthesis by site-directed saturation mutagenesis.
α-Amino acid ester hydrolases (AEHs) catalyze the synthesis of β-lactam antibiotics containing an α-amino group with decreased activity toward antibiotics with a p-hydroxyl group. The AEH gene from Xanthomonas rubrillineans was cloned and expressed in Escherichia coli. Based on the crystal structure of the AEH and cefprozil complex, 13 residues not directly involved in substrate recognition were mutated individually. The resulting ~1,300 mutants were screened for activity using cefprozil as a model product based on spectrophotometric assay in a 96-well format. Mutants with improved cefprozil synthetic activity revealed the particular importance of positions 87, 131 and 175 for specificity. The mutant V131S with the highest initial rates of synthesis toward three p-hydroxyl cephalosporins showed 23 %, 17 % and 64 % increase in maximum product accumulation of cefadroxil, cefprozil and cefatrizine, respectively.
College of Life Sciences, Sichuan University, Chengdu 610064, China.
Li-Juan
LJ
Ye
Lu
L
Wang
Yue
Y
Pan
Yi
Y
Cao
D002265:Carboxylic Ester Hydrolases / Q000235:genetics* / Q000378:metabolism*; D002511:Cephalosporins / Q000096:biosynthesis*; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed / Q000379:methods*; D011487:Protein Conformation; D013379:Substrate Specificity; D014974:Xanthomonas / Q000201:enzymology* / Q000235:genetics
D002511:Cephalosporins; D002265:Carboxylic Ester Hydrolases; C058058:alpha-amino acid esterase