The 2-oxo-1,2-dihydroquinoline 8-monooxygenase from Pseudomonas putida 86 comprises two components with four redox active sites necessary for activity. We present an EPR characterization of the iron-sulfur centres in the purified reductase and oxygenase component of this novel enzyme system. The oxygenase component was identified as a Rieske [2Fe2S] protein on the basis of its characteristic EPR spectrum with gz,y,x = 2.01, 1.91, 1.76 and gav = 1.893. The reductase component, an iron-sulfur flavoprotein, contained a [2Fe2S] cluster with gz,y,x = 2.03, 1.94, 1.89 and the average g-value (gav) of 1.953, typical of a ferredoxin-type centre. In redox titrations at pH 7, the midpoint potentials were determined to be -180 mV +/- 30 mV and -100 mV +/- 10 mV for the reductase and oxygenase component, respectively. A detailed comparison to other multicomponent enzyme systems is presented pointing out the EPR and redox properties of the FeS centres involved.
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