Background: OXA-58 is a carbapenem-hydrolyzing class D -lactamase (CHDL) found in Acinetobacter baumannii. Results: OXA-58 exploits a carbamylated lysine in its catalysis. The deacylating water molecule comes from the ␣-face. Conclusion: CHDLs employ the same hydrolytic machinery as oxacillinases. Structural changes in the active site may lead to imipenem hydrolysis. Significance: This study provides insights for the design of CHDL inactivators.
Lineweaver-Burk plot analysis is the most widely used method to determine enzyme kinetic parameters. In the spectrophotometric determination of enzyme activity using the Lineweaver-Burk plot, it is necessary to find a wavelength at which only the substrate or the product has absorbance without any spectroscopic interference of the other reaction components. Moreover, in this method, different initial concentrations of the substrate should be used to obtain the initial velocities required for Lineweaver-Burk plot analysis. In the present work, a multi-wavelength model-based method has been developed and validated to determine Michaelis-Menten constants for some enzyme reactions. In this method, a selective wavelength region and several experiments with different initial concentrations of the substrate are not required. The absorbance data of the kinetic assays are fitted by non-linear regression coupled to the numeric integration of the related differential equation. To indicate the applicability of the proposed method, the Michaelis-Menten constants for the oxidation of phenanthridine, 6-deoxypenciclovir and xanthine by molybdenum hydroxylases were determined using only a single initial concentration of the substrate, regardless of any spectral overlap.
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