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It has been firmly established that humans excrete a small but steady amount of the isoquinoline alkaloid morphine in their urine. It is unclear whether it is of dietary or endogenous origin. There is no doubt that a simple isoquinoline alkaloid, tetrahydropapaveroline (THP), is found in human and rodent brain as well as in human urine. This suggests a potential biogenetic relationship between both alkaloids. Unlabeled THP or [1,3,4-D₃]-THP was injected intraperitoneally into mice and the urine was analyzed. This potential precursor was extensively metabolized (96%). Among the metabolites found was the phenol-coupled product salutaridine, the known morphine precursor in the opium poppy plant. Synthetic [7D]-salutaridinol, the biosynthetic reduction product of salutaridine, injected intraperitoneally into live animals led to the formation of [7D]-thebaine, which was excreted in urine. [N-CD₃]-thebaine was also administered and yielded [N-CD₃]-morphine and the congeners [N-CD₃]-codeine and [N-CD₃]-oripavine in urine. These results show for the first time that live animals have the biosynthetic capability to convert a normal constituent of rodents, THP, to morphine. Morphine and its precursors are normally not found in tissues or organs, presumably due to metabolic breakdown. Hence, only that portion of the isoquinoline alkaloids excreted in urine unmetabolized can be detected. Analysis of urine by high resolution-mass spectrometry proved to be a powerful method for tracking endogenous morphine and its biosynthetic precursors.

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. Neopinone isomerase catalyzes the isomerization of the opiate alkaloid neopinone to codeinone, driving the biosynthesis of codeine and morphine and preventing accumulation of their isomers neopine and neomorphine.

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. Opiates—the gold standard for pain relief—are currently produced by extraction from opium poppies. Here the authors show that bacteria can serve as an efficient and flexible platform for the production of opiates by demonstrating the total synthesis of Thebaine and hydrocodone from stepwise fermentation in E. coli .

Metabolic engineering of yeast to incorporate plant and bacterial enzymes that construct and decorate morphine, along with spatial engineering to enable a spontaneous chemical reaction, provides strains capable of producing up to 130 mg/l of 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.

A fusion protein containing P450 and aldo-keto reductase domains is shown to catalyze reticuline isomerization, the critical branch point between the noscapine and morphine biosynthetic pathways. This discovery completes the enzymatic route to morphine and related compounds. 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.

Immunofluorescence labeling and shotgun proteomics were used to establish the cell type′specific localization of morphine biosynthesis in opium poppy (Papaver somniferum). Polyclonal antibodies for each of six enzymes involved in converting (R)-reticuline to morphine detected corresponding antigens in sieve elements of the phloem, as described previously for all upstream enzymes transforming (S)-norcoclaurine to (S)-reticuline. Validated shotgun proteomics performed on whole-stem and latex total protein extracts generated 2031 and 830 distinct protein families, respectively. Proteins corresponding to nine morphine biosynthetic enzymes were represented in the whole stem, wherease only four of the final five pathway enzymes were detected in the latex. Salutaridine synthase was detected in the whole stem, but not in the latex subproteome. The final three enzymes converting thebaine to morphine were among the most abundant active latex proteins despite a limited occurrence in laticifers suggested by immunofluorescence labeling. Multiple charge isoforms of two key O-demethylases in the latex were revealed by two-dimensional immunoblot analysis. Salutaridine biosynthesis appears to occur only in sieve elements, whereas conversion of thebaine to morphine is predominant in adjacent laticifers, which contain morphine-rich latex. Complementary use of immunofluorescence labeling and shotgun proteomics has substantially resolved the cellular localization of morphine biosynthesis in opium poppy.

A plant mutant that fails to accumulate morphine provides a genetic clue to identifying the last two enzymes in this alkaloid biosynthetic pathway. Surprisingly, the proteins are non-heme dioxygenases, thus expanding the range of this versatile class of catalysts. Two previously undetected enzymes involved in morphine biosynthesis and unique among plants to opium poppy have been identified as non-heme dioxygenases, in contrast to the functionally analogous cytochrome P450s found in mammals. We used functional genomics to isolate thebaine 6-O-demethylase (T6ODM) and codeine O-demethylase (CODM), the only known 2-oxoglutarate/Fe( II )-dependent dioxygenases that catalyze O-demethylation. Virus-induced gene silencing of T6ODM and CODM in opium poppy efficiently blocked metabolism at thebaine and codeine, respectively.

Papaver somniferum L., a medicinal plant renowned for its pharmaceutical alkaloids, has captivated scientific interest due to its rich secondary metabolite profile. This study explores a novel approach to manipulating alkaloid biosynthesis pathways by integrating virus‐induced gene silencing (VIGS) with macerozyme enzyme pretreatment. Targeting key genes in the benzylisoquinoline alkaloid (BIA) pathway (CODM, T6ODM, COR, DIOX2), the research aimed to elucidate the transformative potential of enzymatic preconditioning in somatic embryo cultures. To address the cell wall barrier, a known limitation in genetic manipulation, macerozyme pretreatment was employed, significantly enhancing gene silencing efficacy. Quantitative reverse transcription PCR analyses revealed significant alterations in gene expression profiles with macerozyme pretreatment, whereas no changes were observed in its absence. The T6ODM + DIOX combination was the most effective, reducing CODM, T6ODM, and DIOX2 expression by 72%, 65%, and 60%, respectively. Conversely, T6ODM expression increased by up to 107% in the CODM treatment. Notably, COR expression displayed dual regulatory dynamics, with suppression (47% decrease in T6ODM + DIOX) and enhancement (49% increase in CODM+DIOX) observed under different conditions. These findings underscore the complex interplay of gene regulation in the morphine biosynthesis pathway. This study highlights the critical role of macerozyme enzymatic pretreatment in overcoming cell wall barriers, enabling effective VIGS applications in somatic suspension cultures. The combination of VIGS and enzymatic pretreatment provides a robust platform for targeted metabolic engineering, offering insights into the regulation of morphine biosynthesis and paving the way for advancements in pharmaceutical alkaloid production and functional genomics in medicinal plants.

Recently, our laboratory demonstrated that human neuroblastoma cells (SH-SY5Y) are capable of synthesizing morphine, the major active metabolite of opium poppy. Now our experiments are further substantiated by extending the biochemical studies to the entire morphine pathway in this human cell line. L-[1,2,3-13C3]- and [ring-2′,5′,6′-2H3]dopa showed high isotopic enrichment and incorporation in both the isoquinoline and the benzyl moiety of the endogenous morphine. [2,2-2H2]Dopamine, however, was exclusively incorporated only into the isoquinoline moiety. Neither the trioxygenated (R,S)-[1,3-13C2]norcoclaurine, the precursor of morphine in the poppy plant, nor (R)-[1,3,4-2H3]norlaudanosoline showed incorporation into endogenous morphine. However, (S)-[1,3,4-2H3]norlaudanosoline furnished a good isotopic enrichment and the loss of a single deuterium atom at the C-9 position of the morphine molecule, indicating that the change of configuration from (S)- to (R)-reticuline occurs via the intermediacy of 1,2-dehydroreticuline. Additional feeding experiments with potential morphinan precursors demonstrated substantial incorporation of [7-2H]salutaridinol, but not 7-[7-2H]episalutaridinol, and [7-2H,N- C2H3]oripavine, and [6-2H]codeine into morphine. Human morphine biosynthesis involves at least 19 chemical steps. For the most part, it is a reflection of the biosynthesis in opium poppy; however, there is a fundamental difference in the formation of the key intermediate (S)-reticuline: it proceeds via the tetraoxygenated initial isoquinoline alkaloid (S)-norlaudanosoline, whereas the plant morphine biosynthesis proceeds via the trioxygenated (S)-norcoclaurine. Following the plant biosynthetic pathway, (S)-reticuline undergoes a change of configuration at C-1 during its transformation to salutaridinol and thebaine. From thebaine, there is a bifurcate pathway leading to morphine proceeding via codeine or oripavine, in both plants and mammals.

Combined with other advances, researchers predict that it will be only a few years - or even months - before a single engineered yeast strain can complete the entire process. Besides giving biologists the power to tinker with the morphine-production process, the advance could lead to more-effective, less addictive and cheaper painkillers that could be brewed under tight controls in fermentation vats.