Exploring antibiotic resistance based on enzyme hydrolysis by microcalorimetry: Part IV. Determination of thermokinetic parameters of D-Ala-D-Ala hydrolysis with dipeptidase VanX

In an effort to explore antibiotic resistance based on enzyme hydrolysis, the thermodynamic parameters of the D-Ala-D-Ala hydrolysis catalyzed by dipeptidase VanX and occurred in Gram-positive vancomycin-resistant pathogens were determined by microcalorimetry. The values of activation free energy DG61⁄4 are 87.140 ± 0.055, 88.413 ± 0.067, 89.611 ± 0.051, and 90.823 ± 0.042 kJ mol at 293.15, 298.15, 303.15, and 308.15 K, respectively, activation enthalpy DHh 6 1⁄4 is 15.332 ± 0.006 kJ mol , activation entropy DS6 1⁄4 is -245.02 ± 0.20 J mol -1 K, apparent activation energy E is 17.830 kJ mol, and the reaction order is 1.5. These thermodynamic data reveal that D-Ala-D-Ala hydrolysis with VanX is an exothermic and spontaneous reaction and has an approximative reaction rate with the imipenem hydrolysis with metallo-b-lactamase ImiS in vitro.