Archives of Biochemistry and Biophysics

The kinetics of Mnoxalate formation and decay were investigated in reactions catalyzed by manganese peroxidase (MnP) from the basiomycete Ceriporiopsis subvermispora in the absence of externally added hydrogen peroxide. A characteristic lag observed in the formation of this complex was shortened by glyoxylate or catalytic amounts of Mn or hydrogen peroxide. MnP titers had a minor effect on this lag and did not influence the decay rate of the complex. In contrast, Mn and oxalate drastically affected maximal concentrations of the Mnoxalate complex formed, the decay of which was accelerated at high M n levels. The highest concentration of complex was obtained at pH 4.0, whereas an inverse relationship was found between the pH of the reaction and the decay rate of the complex with MnP present. In the absence of MnP, the best fit for the decay kinetics of the complex gave an order of 3/2 at concentrations in the range of 30-100 μM, with a k obs = 0.012 min -1 M -0.5 at pH 4.0. The rate constant increases at lower pH values and decreases at high oxalate concentrations. The physiological relevance of these findings is discaused. © 1998 Academic Press