Quinine 3-monooxygenase () is an enzyme that catalyzes the chemical reaction
The four substrates of this enzyme are quinine, reduced nicotinamide adenine dinucleotide phosphate (NADPH), oxygen, and a proton. Its products are 3-hydroxyquinine, oxidised NADP<sup>+</sup>, and water.
This enzyme is a cytochrome P450 protein containing heme. This oxidoreductase, which uses molecular oxygen as oxidant is in a group with systematic name quinine,NADPH:oxygen oxidoreductase. This enzyme is also called quinine 3-hydroxylase. It is present in human liver, where it is involved in the metabolism of quinine.
As of late 2007, 5 structures have been solved for this class of enzymes, with PDB accession codes , , , , and .