Exploring antibiotic resistance based on enzyme hydrolysis by microcalorimetry

Abstract

In an effort to understand the reactions of antibiotics hydrolysis with metallo-β-lactamases (MβLs), the thermokinetic parameters of cefazolin hydrolysis with B1 subclass MβL CcrA from Bacteroides fragilis were determined by microcalorimetric method. The values of activation free energy $\Updelta G_{ \ne }^{\theta }$ are 88.032 ± 0.038, 89.075 ± 0.025, 90.095 ± 0.034, and 91.261 ± 0.044 kJ mol⁻¹ at 293.15, 298.15, 303.15, and 308.15 K, respectively, the activation enthalpy $\Updelta H_{ \ne }^{\theta }$ is 25.278 ± 0.005 kJ mol⁻¹, the activation entropy $\Updelta S_{ \ne }^{\theta }$ is −213.99 ± 0.14 J mol⁻¹ K⁻¹, the apparent activation energy E is 27.776 kJ mol⁻¹, and the reaction order is 1.4. The results indicated that the cefazolin hydrolysis with CcrA is an exothermic and spontaneous reaction. An association between the thermokinetic and kinetic parameters was revealed, which is that the catalytic constant K _cat increase with increase in $\Updelta H_{ \ne }^{\theta }$.