Structure of cephalosporin acylase in complex with glutaryl-7-aminocephalosporanic acid and glutarate: insight into the basis of its substrate specificity.
BACKGROUND
Semisynthetic cephalosporins are primarily synthesized from 7-aminocephalosporanic acid (7-ACA), which is obtained by environmentally toxic chemical deacylation of cephalosporin C (CPC). Thus, the enzymatic conversion of CPC to 7-ACA by cephalosporin acylase (CA) would be of great interest. However, CAs use glutaryl-7-ACA (GL-7-ACA) as a primary substrate and the enzyme has low turnover rates for CPC.


RESULTS
The binary complex structures of CA with GL-7-ACA and glutarate (the side-chain of GL-7-ACA) show extensive interactions between the glutaryl moiety of GL-7-ACA and the seven residues that form the side-chain pocket. These interactions explain why the D-alpha-aminoadipyl side-chain of CPC yields a poorer substrate than GL-7-ACA.


CONCLUSIONS
This understanding of the nature of substrate specificity may be useful in the design of an enzyme with an improved performance for the conversion of CPC to 7-ACA. Additionally, the catalytic mechanism of the deacylation reaction was revealed by the ligand bound structures.
Kim
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Y
School of Chemical Engineering, Yeungnam University, South Korea. ykim1@yu.ac.kr
Hol
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WG
D002384:Catalysis; D002511:Cephalosporins / Q000737:chemistry*; D004926:Escherichia coli; D005977:Glutarates / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D010399:Penicillin Amidase / Q000737:chemistry*; D011487:Protein Conformation; D013379:Substrate Specificity
D002511:Cephalosporins; D005977:Glutarates; D008024:Ligands; C081063:glutaryl-7-aminocephalosporanic acid; D010399:Penicillin Amidase