Feb 25, 1989

Manganese peroxidase from the lignin-degrading basidiomycete Phanerochaete chrysosporium. Transient state kinetics and reaction mechanism

The Journal of Biological Chemistry
H WariishiM H Gold


Stopped-flow techniques were used to investigate the kinetics of the formation of manganese peroxidase compound I (MnPI) and of the reactions of MnPI and manganese peroxidase compound II (MnPII) with p-cresol and MnII. All of the rate data were obtained from single turnover experiments under pseudo-first order conditions. In the presence of H2O2 the formation of MnPI is independent of pH over the range 3.12-8.29 with a second-order rate constant of (2.0 +/- 0.1) x 10(6) M-1 s-1. The activation energy for MnPI formation is 20 kJ mol-1. MnPI formation also occurs with organic peroxides such as peracetic acid, m-chloroperoxybenzoic acid, and p-nitroperoxybenzoic acid with second-order rate constants of 9.7 x 10(5), 9.5 x 10(4), and 5.9 x 10(4) M-1 s-1, respectively. The reactions of MnPI and MnPII with p-cresol strictly obeyed second-order kinetics. The second-order rate constant for the reaction of MnPII with p-cresol is extremely low, (9.5 +/- 0.5) M-1 s-1. Kinetic analysis of the reaction of MnII with MnPI and MnPII showed a binding interaction with the oxidized enzymes which led to saturation kinetics. The first-order dissociation rate constants for the reaction of MnII with MnPI and MnPII are (0.7 +/- 0.1) and (0.14 +/- 0.01)...Continue Reading

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4-cresol, sodium salt

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