Oxidation of 1,5-benzodiazepine oximes catalysed by peroxidases

Oxidation of 1,3,4,5-tetrahydro-2H-1,5-benzodiazepine oximes catalysed by horseradish peroxidase (HRP) and recombinant Coprinus cinereus peroxidase (rCiP) was studied spectrophotometrically. The reaction rate dependences on the substrate and hydrogen peroxide concentrations were investigated; the values of apparent KM and Vmax, catalytic, oxidation and reduction constants (kcat, kox and kred, respectively) were calculated. The reactivity constants for the reactions catalysed by rCiP were higher than those for the HRP. Since oximes can have different structures depending on pH, the influence of pH on the rate of oxidation of compounds was studied. The dependences of the oxidation rate of the investigated oximes on the pH of the buffer solution were determined, and the pKa values of the amino acids of peroxidases responsible for the rate of catalysis were obtained. The HRP activity dependence on pH has a classical bell-shaped character, while rCiP dependence has a complex character.