Publications

• Stereochemical inversion of (S)-reticuline by a cytochrome P450 fusion in opium poppy.

  Farrow S.C., Hagel J.M., Beaudoin G.A., Burns D.C., Facchini P.J.

  The gateway to morphine biosynthesis in opium poppy (Papaver somniferum) is the stereochemical inversion of (S)-reticuline since the enzyme yielding the first committed intermediate salutaridine is specific for (R)-reticuline. A fusion between a cytochrome P450 (CYP) and an aldo-keto reductase (AK ... >> More

  The gateway to morphine biosynthesis in opium poppy (Papaver somniferum) is the stereochemical inversion of (S)-reticuline since the enzyme yielding the first committed intermediate salutaridine is specific for (R)-reticuline. A fusion between a cytochrome P450 (CYP) and an aldo-keto reductase (AKR) catalyzes the S-to-R epimerization of reticuline via 1,2-dehydroreticuline. The reticuline epimerase (REPI) fusion was detected in opium poppy and in Papaver bracteatum, which accumulates thebaine. In contrast, orthologs encoding independent CYP and AKR enzymes catalyzing the respective synthesis and reduction of 1,2-dehydroreticuline were isolated from Papaver rhoeas, which does not accumulate morphinan alkaloids. An ancestral relationship between these enzymes is supported by a conservation of introns in the gene fusions and independent orthologs. Suppression of REPI transcripts using virus-induced gene silencing in opium poppy reduced levels of (R)-reticuline and morphinan alkaloids and increased the overall abundance of (S)-reticuline and its O-methylated derivatives. Discovery of REPI completes the isolation of genes responsible for known steps of morphine biosynthesis. << Less

  Nat Chem Biol 11:728-732(2015) [PubMed] [EuropePMC]

• Morphinan biosynthesis in opium poppy requires a P450-oxidoreductase fusion protein.

  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., Graham I.A.

  Morphinan alkaloids from the opium poppy are used for pain relief. The direction of metabolites to morphinan biosynthesis requires isomerization of (S)-to (R)-reticuline. Characterization of high-reticuline poppy mutants revealed a genetic locus, designated STORR [(S)-to (R)-reticuline] that encod ... >> More

  Morphinan alkaloids from the opium poppy are used for pain relief. The direction of metabolites to morphinan biosynthesis requires isomerization of (S)-to (R)-reticuline. Characterization of high-reticuline poppy mutants revealed a genetic locus, designated STORR [(S)-to (R)-reticuline] that encodes both cytochrome P450 and oxidoreductase modules, the latter belonging to the aldo-keto reductase family. Metabolite analysis of mutant alleles and heterologous expression demonstrate that the P450 module is responsible for the conversion of (S)-reticuline to 1,2-dehydroreticuline, whereas the oxidoreductase module converts 1,2-dehydroreticuline to (R)-reticuline rather than functioning as a P450 redox partner. Proteomic analysis confirmed that these two modules are contained on a single polypeptide in vivo. This modular assembly implies a selection pressure favoring substrate channeling. The fusion protein STORR may enable microbial-based morphinan production. << Less

  Science 349:309-312(2015) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• 1,2-Dehydroreticuline synthase, the branch point enzyme opening the morphinan biosynthetic pathway.

  Hirata K., Poeaknapo C., Schmidt J., Zenk M.H.

  A synthase which oxidizes (S)-reticuline to 1,2-dehydroreticuline has been found to occur in seedlings of opium poppy (Papaver somniferum L.). Due to its instability, this enzyme could only be partly purified (ca. 5-fold enrichment). Partial characterization at this stage of purification showed th ... >> More

  A synthase which oxidizes (S)-reticuline to 1,2-dehydroreticuline has been found to occur in seedlings of opium poppy (Papaver somniferum L.). Due to its instability, this enzyme could only be partly purified (ca. 5-fold enrichment). Partial characterization at this stage of purification showed that it does not need a redox cofactor and accepts both (S)-reticuline and (S)-norreticuline as substrates. [1-(2)H, (13)C]-(R,S)-reticuline was enzymatically converted into [1-(13)C]-dehydroreticuline, which has been identified by mass spectrometry. Release of the hydrogen atom in position C-1 of the isoquinoline alkaloid during the oxidative conversion, was exploited as a sensitive assay system for this enzyme. The enzyme has a pH optimum of 8.75, a temperature optimum of 37 degrees C and the apparent K(M) value for the substrate reticuline was shown to be 117 microM. Moreover it could be demonstrated by sucrose density gradient centrifugation that the enzyme is located in vesicles of varying size. In combination with the previously discovered strictly stereoselective and NADPH dependent 1,2-dehydroreticuline reductase the detection of this enzyme, the 1,2-dehydroreticuline synthase, provides the necessary inversion of configuration and completes the pathway from two molecules of L-tyrosine via (S)-norcoclaurine to (R)-reticuline in opium poppy involving a total number of 11 enzymes. << Less

  Phytochemistry 65:1039-1046(2004) [PubMed] [EuropePMC]