Converts (3-methyl-)-quinoline to (3-methyl-)2-oxo-1,2-dihydroquinoline. A + H2O + quinoline = AH2 + quinolin-2(1H)-one Binds 1 Mo-molybdopterin cytosine dinucleotide (Mo-MCD) cofactor per subunit. Xenobiotic degradation; quinoline degradation. Heterohexamer of two alpha chains, two beta chains, and two gamma chains.