In plants, adverse conditions often induce an increase in reactive oxygen species (ROS) such as hydrogen peroxide (H 2 O 2). H 2 O 2 is reduced to water, and thus becomes detoxified by enzymes such as Cytisus multiflorus peroxidase (CMP). Here, the steady-state kinetics of the H 2 O 2-supported oxidation of different organic substrates by CMP was investigated. Analysis of the initial rates vs. H 2 O 2 and reducing substrate concentrations proved to be consistent with a substrate-inhibited Ping-Pong Bi–Bi reaction mechanism. The phenomenological approach expresses the peroxidase Ping-Pong mechanism in the form of the Michaelis–Menten equation and affords an interpretation of the effects in terms of the kinetic parameters K m H 2 O 2, K m AH 2, k cat, K SI H 2 O, K SI AH 2 and of the microscopic rate constants, k 1 and k 3, of the shared three-step catalytic cycle of peroxidases.