CuI-semiquinone radical species in plant copper-amine oxidases.

The intermediate CuI-semiquinone radical species in the catalytic mechanism of copper-amine oxidase from Lens esculenta and Pisum sativum seedlings has been studied by optical, Raman resonance and ESR spectroscopies and by stopped-flow and temperature-jump measurements. Treatment of highly purified enzyme preparations with good, poor or suicide substrates, under anaerobic and aerobic conditions, at different pH values and temperatures, makes it possible to generate, detect and characterize this free radical intermediate.