title: Determination of the second autoproteolytic cleavage site of cephalosporin C acylase and the effect of deleting its flanking residues in the α-C-terminal region.
abstract: Self-activation through two-step intra-molecular cleavages is of great importance for the synthesis of mature and functional cephalosporin acylase in the N-terminal nucleophile (Ntn) hydrolase superfamily. A synthetic gene for cephalosporin C acylase (sCPCAcy) from Pseudomonas sp. SE83 was overexpressed, and the self-activated sCPCAcy was produced in Escherichia coli JM109(DE3)/pET28-sCPCAcy. The first autoproteolytic cleavage site of Pre-sCPCAcy was determined to be G239-S240 according to the common features of Ntn hydrolases. The second cleavage site was identified as A232-S233 by C-terminus tandem MS/MS analysis of the purified α-subunit, which released a 7-aa spacer peptide with the generation of the α and β subunits of the mature sCPCAcy. The effect of the cleavage-site-flanking residues in the α-C-terminal region of sCPCAcy on its activation and characteristics was further evaluated. Residue G229 was found to be crucial for the first cleavage of Pre-sCPCAcy. Deletions in the α-C-terminal region were performed, and 14 mutant proteins were constructed. The majority of the fragment-deleted mutant proteins completely lost their activity due to failure of the first autocleavage, but this loss was not observed in mutant proteins D2 (227-AM-228 deletion) and D4 (212-ADLA-215 deletion), which formally activated into mature sCPCAcy with high activity. The Kcat/Km values of mutant proteins D2 and D4 were 46% and 102% higher than that of the original control, respectively.
authors.affiliation: Institute of Biochemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, PR China.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Institute of Biochemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, PR China. Electronic address: yuhm@tsinghua.edu.cn.
authors.forename: Huimin
authors.initials: H
authors.lastname: Yu
authors.affiliation: Institute of Biochemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, PR China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Biological Science and Technology, University of Science and Technology Beijing, Beijing 100083, PR China.
authors.forename: Hui
authors.initials: H
authors.lastname: Luo
authors.affiliation: Institute of Biochemical Engineering, Department of Chemical Engineering, Tsinghua University, Beijing 100084, PR China.
authors.forename: Zhongyao
authors.initials: Z
authors.lastname: Shen
mesh_terms: D002511:Cephalosporins / Q000096:biosynthesis* / Q000737:chemistry; D004926:Escherichia coli; D015964:Gene Expression Regulation, Bacterial; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010399:Penicillin Amidase / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D017434:Protein Structure, Tertiary; D011549:Pseudomonas / Q000201:enzymology*; D053719:Tandem Mass Spectrometry
chemical_list: D002511:Cephalosporins; C025163:cephalosporin C; D010399:Penicillin Amidase
keywords: C-terminus tandem MS/MS; Cephalosporin C acylase; Cleavage-site-flanking residue; Fragment deletion; Spacer peptide