In enzymology, a morphine 6-dehydrogenase () is an enzyme that catalyzes the chemical reaction
The 3 substrates of this enzyme are morphine, NAD<sup>+</sup>, and NADP<sup>+</sup>, whereas its 4 products are morphinone, NADH, NADPH, and H<sup>+</sup>.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD<sup>+</sup> or NADP<sup>+</sup> as acceptor. The systematic name of this enzyme class is morphine:NAD(P)<sup>+</sup> 6-oxidoreductase. Other names in common use include naloxone reductase, and reductase, naloxone. This enzyme participates in alkaloid biosynthesis i. This enzyme has at least one effector, Mercaptoethanol.