Ethylene enhances reactivity of superoxide with peroxidase to form the oxy-ferrous complex

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Abstract
Ethylene and its analogs acetylene, carbon monoxide and propylene inhibited the rate of oxidation of IAA by peroxidase. Annulment of this effect by addition of superoxide dismutase showed that inhibition occurred only in the presence of the superoxide anion radical (O2-.cntdot.). Kinetic and spectral data established that ethylene and its analogs enhanced markedly the rate of reaction of O2-.cntdot. with peroxidase. This reaction resulted in the formation of compound III, an oxy-ferrous complex of peroxidase. In the presence of IAA, the interaction between ethylene, peroxidase and O2-.cntdot.activated the reduced peroxidase .dblarw. compound III shuttle. O2-.cntdot. is a major product of this shuttle, and compound III constitutes the dominant steady-state form of peroxidase. These interactions may help to explain the mechanism of action of ethylene as a plant growth regular.