Involved in the terminal step of the biosynthesis of quinolone which in addition to serve as a potent signal for quorum sensing, chelates iron and promotes the formation of membrane vesicles (MVs). Catalyzes the hydroxylation of 2-heptyl-4-quinolone (C7-HHQ) to yield 2-heptyl-3-hydroxy-4-quinolone (PQS). PqsH is also able to hydroxylate HHQ analogs having alkyl side-chain lengths of 3 (C3-HHQ), 5 (C5-HHQ) and 9 (C9-HHQ) carbons, however catalytic efficiencies are significantly reduced for substrates with alkyl side-chain lengths below 7 carbons. 2-heptyl-4(1H)-quinolone + H(+) + NADH + O2 = 2-heptyl-3-hydroxy-4(1H)-quinolone + H2O + NAD(+) kcat is 1.2 min(-1) for hydroxylation with oxygen (at 37 degrees Celsius). kcat is 2.7 min(-1) for hydroxylation with 2-heptyl-4-quinolone (at 37 degrees Celsius). kcat is 3.2 min(-1) for hydroxylation with NADH (at 37 degrees Celsius). kcat is 3.8 min(-1) for hydroxylation with NADPH (at 37 degrees Celsius). By LasR. Oxygen is essential for PQS production and anaerobic P.aeruginosa produces undetectable levels of MVs and display reduced killing of prokaryotic and eukaryotic cells. Belongs to the 3-hydroxybenzoate 6-hydroxylase family.