Neopinone isomerase is involved in codeine and morphine biosynthesis in opium poppy.

The isomerization of neopinone to codeinone is a critical step in the biosynthesis of opiate alkaloids in opium poppy. Previously assumed to be spontaneous, the process is in fact catalyzed enzymatically by neopinone isomerase (NISO). Without NISO the primary metabolic products in the plant, in engineered microbes and in vitro are neopine and neomorphine, which are structural isomers of codeine and morphine, respectively. Inclusion of NISO in yeast strains engineered to convert thebaine to natural or semisynthetic opiates dramatically enhances formation of the desired products at the expense of neopine and neomorphine accumulation. Along with thebaine synthase, NISO is the second member of the pathogenesis-related 10 (PR10) protein family recently implicated in the enzymatic catalysis of a presumed spontaneous conversion in morphine biosynthesis.

Total biosynthesis of opiates by stepwise fermentation using engineered Escherichia coli.

Opiates such as morphine and codeine are mainly obtained by extraction from opium poppies. Fermentative opiate production in microbes has also been investigated, and complete biosynthesis of opiates from a simple carbon source has recently been accomplished in yeast. Here we demonstrate that Escherichia coli serves as an efficient, robust and flexible platform for total opiate synthesis. Thebaine, the most important raw material in opioid preparations, is produced by stepwise culture of four engineered strains at yields of 2.1 mg l(-1) from glycerol, corresponding to a 300-fold increase from recently developed yeast systems. This improvement is presumably due to strong activity of enzymes related to thebaine synthesis from (R)-reticuline in E. coli. Furthermore, by adding two genes to the thebaine production system, we demonstrate the biosynthesis of hydrocodone, a clinically important opioid. Improvements in opiate production in this E. coli system represent a major step towards the development of alternative opiate production systems.

A microbial biomanufacturing platform for natural and semisynthetic opioids.

Opiates and related molecules are medically essential, but their production via field cultivation of opium poppy Papaver somniferum leads to supply inefficiencies and insecurity. As an alternative production strategy, we developed baker's yeast Saccharomyces cerevisiae as a microbial host for the transformation of opiates. Yeast strains engineered to express heterologous genes from P. somniferum and bacterium Pseudomonas putida M10 convert thebaine to codeine, morphine, hydromorphone, hydrocodone and oxycodone. We discovered a new biosynthetic branch to neopine and neomorphine, which diverted pathway flux from morphine and other target products. We optimized strain titer and specificity by titrating gene copy number, enhancing cosubstrate supply, applying a spatial engineering strategy and performing high-density fermentation, which resulted in total opioid titers up to 131 mg/l. This work is an important step toward total biosynthesis of valuable benzylisoquinoline alkaloid drug molecules and demonstrates the potential for developing a sustainable and secure yeast biomanufacturing platform for opioids.

Localization of endogenous morphine-like compounds in the mouse spinal cord.

Morphine, codeine, morphine-6-glucuronide, and morphine-3-glucuronide are synthesized de novo in mammalian cells and in the central nervous system. Knowledge on endogenous morphine-like compound distribution in the adult mouse brain has been recently improved, and new hypotheses have been suggested about the potential implications in brain physiology. Endogenous morphine-like compounds have been shown to be synthesized in the spinal cord, but their localization is unknown. Here we describe the distribution of endogenous morphine-like compounds (morphine and/or its glucuronides and/or codeine) in the adult mouse spinal cord using a well-validated antibody. By using different microscopy approaches, we found the presence of morphine, codeine, or morphine glucuronides in γ-aminobutyric acid (GABA)-ergic neurons and astrocytes of the spinal cord. Whereas GABAergic neurons containing endogenous morphine-like compounds were located primarily in the ventral horn, astrocytes that were labeled for morphine-like compounds were found throughout the gray matter and the white matter. Our study demonstrates the possibility that endogenous morphine-like compounds in the central nervous system have other functions beyond their analgesic functions.

Genetic transmission of cytochrome P450 2D6 (CYP2D6) ultrarapid metabolism: implications for breastfeeding women taking codeine.

The pro-drug codeine is commonly prescribed for postpartum pain relief in North America. The safety of codeine during breastfeeding is related in part to the extent of the active morphine metabolite catalyzed from codeine via the cytochrome P450 2D6 (CYP2D6) enzyme. In mothers who have greater than two functional copies of the CYP2D6 gene (CYP2D6 ultrarapid metabolism phenotype; UM) a substantially higher proportion of morphine is produced. Label changes on codeine-containing medications will highlight the risks associated with this genotype for breastfeeding mothers, but are not supported by translation strategies on how to incorporate this pharmacogenetic knowledge into clinical practice. To address the immediate issue of CYP2D6 UM inheritance in family members of a breastfed infant who succumbed to fatal opioid intoxication and whose codeine-prescribed mother was a CYP2D6 UM, we constructed a pedigree. While the pedigree approach is helpful to aid diagnosis, identify other at risk family members, and simplify pharmacogenetic analysis, its clinical usefulness is dependant on an institutional framework which is not available in most centers at this time.

Hairy root induction of Papaver somniferum var. album, a difficult-to-transform plant, by A rhizogenes LBA 9402.

Two strains of Agrobacterium rhizogenes (15834, LBA 9402) and one Agrobacterium tumefaciens strain [GV 3101 (PMP90RK, p35SGUS-2)] and four culture media were tested and compared for their ability to induce hairy root formation on wounded Papaver somniferum L. hypocotyls. Five weeks after the infection with A. rhizogenes LBA 9402, hairy roots appeared on 80% of the hypocotyls maintained in the hormone-free liquid medium. Six hairy-root cultures were established. Transformation was confirmed by polymerase chain reaction analysis. One clone was analysed for its alkaloid production. The total alkaloid content was higher in the transformed roots (0.46+/-0.06% DW) than in the untransformed roots (0.32+/-0.05% DW). The transformed roots accumulated three times more codeine (0.18+/-0.02% DW) than intact roots (0.05+/-0% DW). Moreover, morphine (0.255+/-0.03% DW) and sanguinarine (0.014+/-0% DW) were found in the liquid culture medium.

Identification of the convulsant opiate thebaine in mammalian brain.

The convulsant opiate thebaine, an intermediate of morphine biosynthesis, was purified from bovine brain to homogeneity by gel filtration and high-performance liquid chromatography (HPLC) monitored by a radioimmunoassay. The immunoreactive material behaved identically to standard thebaine in two HPLC systems and was confirmed to be thebaine by combined gas chromatography/mass spectrometry. To our knowledge, the presence of thebaine in mammalian tissue has not been demonstrated previously. Codeine and morphine were also found to exist in ovine brain. The presence of thebaine in ovine brain provides strong evidence that morphine and codeine, in various mammalian tissues, are of endogenous origin and actually biosynthesized from a precursor.

Transformation of thebaine to oripavine, codeine, and morphine by rat liver, kidney, and brain microsomes.

Thebaine, an intermediate of morphine biosynthesis in the poppy plant, Papaver somniferum, was transformed to oripavine, codeine, and morphine by rat liver, kidney, and brain microsomes in the presence of an NADPH-generating system. The formation of morphine, codeine, and oripavine was identified by a specific RIA, HPLC, and GCMS. Thebaine also gave rise to four other compounds, which for the moment are unidentified. NADH dramatically increased the formation of both codeine and morphine when used together with an NADPH-generating system, especially in liver microsomes. NADPH is essential in the formation of oripavine from thebaine and morphine from codeine, while NADH is critical in the conversion of thebaine to codeine and from oripavine to morphine. Carbon monoxide or SKF 525A inhibited the conversion, indicating a role of cytochrome P-450. These results provide evidence for the enzymatic in vitro conversion by mammalian tissues of thebaine to morphine. The pathway is similar to that which exists in plants.

Presence and formation of codeine and morphine in the rat.

Endogenous codeine and morphine were identified in rat brain by immunological determination following HPLC. To demonstrate occurrence of a biosynthetic pathway to morphine in mammals similar to that used by the poppy plant, (+)-salutaridine, (-)-thebaine, and (-)-codeine were administered to rats intravenously. These compounds, which are intermediates in the synthesis of morphine in Papaver somniferum, caused a marked increase in the codeine and morphine levels in rat tissues. This provides evidence for a biosynthetic pathway to morphine in mammalians.

In vitro formation of codeinone from codeine by rat or guinea pig liver homogenate and its acute toxicity in mice.

In vitro metabolism of codeine was investigated by using a 9000 g supernatant fraction of rat or guinea pig liver homogenate. When a mixture of [N-14CH3] and [C-6-3H]codeine was incubated with the rat liver 9000 g supernatant fraction in the presence of NAD, formation of codeinone, morphine and norcodeine was detected. Replacement of NAD with NADP abolished only the formation of codeinone. On the other hand, when the guinea pig liver homogenate was used in the presence of NAD, codeinone was the main metabolite of codeine. NADP was also ineffective in forming codeinone with the guinea pig liver homogenate. The acute toxicity of codeinone was thirty times higher than that of codeine. The roles of codeinone as a metabolic intermediate and in the acute toxicity of codeine are discussed.