||A P-450 (heme-thiolate) cytochrome. The enzyme from Papaver rhoeas (field poppy) is specific for (S)-reticuline and does not act on the (R)-form. The enzyme from Papaver somniferum (opium poppy), which is involved in the biosynthesis of morphine and related alkaloids, forms a fusion protein with EC 184.108.40.206, 1,2-dehydroreticulinium reductase (NADPH), which catalyses the reduction of 1,2-dehydroreticuline to (R)-reticuline, thus forming an epimerase system that converts (S)-reticuline to (R)-reticuline.
||Hirata, K., Poeaknapo, C., Schmidt, J. and Zenk, M.H. 1,2-Dehydroreticuline synthase, the branch point enzyme opening the morphinan biosynthetic pathway. Phytochemistry 65 (2004) 1039–1046. [DOI] [PMID: 15110683]
||Winzer, T., Kern, M., King, A.J., Larson, T.R., Teodor, R.I., Donninger, S.L., Li, Y., Dowle, A.A., Cartwright, J., Bates, R., Ashford, D., Thomas, J., Walker, C., Bowser, T.A. and Graham, I.A. Morphinan biosynthesis in opium poppy requires a P450-oxidoreductase fusion protein. Science 349 (2015) 309–312. [DOI] [PMID: 26113639]
||Farrow, S.C., Hagel, J.M., Beaudoin, G.A., Burns, D.C. and Facchini, P.J. Stereochemical inversion of (S)-reticuline by a cytochrome P450 fusion in opium poppy. Nat. Chem. Biol. 11 (2015) 728–732. [DOI] [PMID: 26147354]