2-OXO-1,2-DIHYDROQUINOLINE 8-MONOOXYGENASE, A 2-COMPONENT ENZYME-SYSTEM FROM PSEUDOMONAS-PUTIDA-86

2-Oxo-1,2-dihydroquinoline 8-monooxygenase, which catalyzes the NADH-d ependent oxygenation of 2-oxo-1,2-dihydroquinoline to 8-hydroxy-2-oxo- 1,2-dihydroquinoline, is the second enzyme in the quinoline degradatio n pathway of Pseudomonas putida 86. This enzyme system consists of two inducible protein components, which were purified, characterized, and identified as reductase and oxygenase. The yellow reductase is a mono meric iron-sulfur flavoprotein (M(r), 38,000), containing flavin adeni ne dinucleotide and plant-type ferredoxin [2Fe-2S]. It transferred ele ctrons from NADH to the oxygenase or to some artificial electron accep ters. The red-brown oxygenase (M(r), 330,000) consists of six identica l subunits (M(r), 55,000) and was identified as an iron-sulfur protein , possessing about six Rieske-type [2Fe-2S] clusters and additional ir on. It was reduced by NADH plus catalytic amounts of reductase. For mo nooxygenase activity, reductase, oxygenase, NADH, molecular oxygen, an d substrate were required. The activity was considerably enhanced by t he addition of polyethylene glycol and Fe2+. 2-Oxo-1,2-dihydroquinolin e 8-monooxygenase revealed a high substrate specificity toward 2-oxo-1 ,2-dihydroquinoline, since none of 25 other tested compounds was conve rted. Based on its physical, chemical, and catalytic properties, we pr esume 2-oxo-1,2-dihydroquinoline 8-monooxygenase to belong to the clas s IB multicomponent non-heme iron oxygenases.