1,2-dehydroreticulinium reductase (NADPH) () is an enzyme that catalyzes the chemical reaction
The three substrates of this enzyme are 1,2-dehydroreticulinium cation, reduced nicotinamide adenine dinucleotide phosphate (NADPH) and a proton. Its products are (R)-reticuline and oxidised NADP<sup>+</sup>. The enzyme does not catalyse the reverse (oxidation) reaction.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-NH group of donors with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is (R)-reticuline:NADP+ oxidoreductase. This enzyme is also called 1,2-dehydroreticulinium ion reductase. It participates in morphinan alkaloid biosynthesis.
In the opium poppy, Papaver somniferum, this enzyme forms a fusion protein with 1,2-dehydroreticuline synthase, which converts (S)-reticuline to reticulinylium cation. The overall result is that the (S) enantiomer of reticuline is converted to {R)-reticuline, which is the precursor of salutaridine, on the pathway to morphine. This gene fusion event has been suggested to evolve only once, about 20 million years ago.