Title
Comparative characterization of CTX-M-64 and CTX-M-14: insights into the structure and catalytic activity of the CTX-M class of enzymes
Author
Dandan He, Jiachi Chiou, Zhenling Zeng, Edward Wai-Chi Chan, Jian-Hua Liu, Sheng Chen
Year
2016
Journal
Antimicrobial Agents and Chemotherapy
Abstract
Clinical isolates producing hybrid CTX-M β-lactamases, presumably due to recombination between the blaCTX-M-15 and blaCTX-M-14 elements, have emerged in recent years. Among the hybrid enzymes, CTX-M-64 and CTX-M-14 displayed the most significant difference in catalytic activity. This study aims to investigate the mechanisms underlying such differential enzymatic activities in order to provide insight into the structure/function relationship of this class of enzymes. Sequence alignment analysis showed that the major differences between the amino acid composition of CTX-M-64 and CTX-M-14 lie at both the N- and C-termini of the enzymes. Single or multiple amino acid substitutions introduced into CTX-M-64 and CTX-M-14 were found to produce only minor effects on hydrolytic functions; such finding is consistent with the notion that the discrepancy between the functional activities of the two enzymes is not the result of only a few amino acid changes, but attributable to interactions between a unique set of amino acid residues in each enzyme. This theory is supported by results of the thermal stability assay, which confirmed that CTX-M-64 is significantly more stable than CTX-M-14. Our data confirmed that, in addition to the important residues located in the active site, residues distal to the active site also contribute to the catalytic activity of the enzyme through stabilizing its structural integrity.
Instrument
J-810
Keywords
Circular dichroism, Secondary structure, Thermal stability, Biochemistry