Research led by biochemist Peter Facchini is huge step toward commercializing efficient, yeast-based production of pain-killing opiates
By Mark Lowey, for the Faculty of Science
A University of Calgary-led research team has discovered the gene for a new protein crucial for naturally and efficiently producing a compound in opium poppy plants used to make opiate pain-killing drugs.
The team found the gene that encodes a previously unknown protein, an enzyme called thebaine synthase, which plays a vital role in catalyzing the production of thebaine in opium poppies. The discovery is a huge step toward commercializing an efficient, inexpensive yeast-based system for manufacturing opiates such as morphine and codeine, says team leader Peter Facchini, professor of biochemistry in the Department of Biological Sciences in the Faculty of Science.
“Thebaine is the gateway to all pharmaceutical opiates. This enzyme, thebaine synthase or THS, is essential to achieve commercially viable production levels of thebaine,” says Facchini, who for 26 years has been investigating how the opium poppy plant makes these compounds.
A system using engineered yeast inserted with thebaine-producing genes also could be used to make valuable semi-synthetic pain-killing medications such as oxycodone and hydrocodone, or naloxone and naltrexone which are essential for treating opioid dependency and overdose.
“The bio-production platform gives you a suite of opportunities to make new compounds that have the same chemical ‘backbone,’ but improved qualities as prescription medicines,” Facchini says.
This includes the potential in the future to produce next-generation pain killers that aren’t addictive like all currently available opiates, he says.
Much of the research was done by three senior scientists — Xue Chen, Jillian Hagel and Limei Chang — working under contact for the UCalgary startup Epimeron Inc., a Calgary-based biotechnology company. Epimeron was created to commercialize technology developed in Facchini’s UCalgary laboratory (he is chief scientific officer and a co-founder along with Hagel).
Several scientists at Intrexon Corp., a San Francisco-based biotechnology firm partnered with Epimeron, also contributed to the research.
“This is a strong example of entrepreneurship at the University of Calgary,” Facchini says. “We continue to demonstrate that you can make groundbreaking discoveries in Calgary, in Alberta, and not only contribute to, but actually lead, an enterprise of crucial importance to the entire world.”
The team’s paper, A Pathogenesis-Related 10 Protein Catalyzes the Final Step in Thebaine Biosynthesis, is published in Nature Chemical Biology, a journal in the top-ranked Nature series of publications.
World dependent on opium poppies for opiates
The opium poppy is the sole source for all opiates used in medicine, and the United Nations and national governments allow crops to be grown in only a few countries.
That makes Canada and the rest of the world dependent on opium poppy crops, about half of which are cultivated in Tasmania, Australia. The remaining crops are grown mostly in India, Turkey and France.
Yields from these crops are always uncertain, due to environmental factors, climate change, disease and pests, Facchini says. “What if there’s a blight — and there have been blights — of the opium poppy crop in Australia?”
Moreover, 95 per cent of the global population has no access to any opiates, he notes. “How do most people in the world manage pain? They don’t.”
A production system using yeast grown in a fermenter and fed cheap carbon (sugar) could provide relatively inexpensive opiates to hundreds of millions of people, he says.
The next steps to achieving such a system are to look for any more missing genes involved in thebaine production, and to get plant-derived genes and enzymes to function optimally in a yeast cell.
Team tracked down ‘missing’ component in thebaine production
The team started looking for a ‘missing’ component in how the opium poppy plant chemically synthesizes thebaine, after observing a problem when trying to produce thebaine in yeast.
They found for the first time an unstable, transient compound involved in the final synthesis step which quickly biodegraded into an unwanted byproduct, resulting in very little thebaine produced.
Thebaine accumulates naturally in specialized cells in the latex of the opium poppy plant — the “milk of the poppy” made famous in the Game of Thrones television series. The team added some extract from the latex to in vitro assay samples and immediately saw increased thebaine production.
“That was really the Eureka! moment, because now you can say there’s a protein in there that’s playing that role,” Facchini says.
The team used classic biochemistry techniques such as protein purification, coupled with state-of-the-art proteomics and gene synthesis to pinpoint the gene and its location — in a novel gene cluster in the opium poppy plant genome.
They then showed the function of thebaine synthase, using ‘gene-silencing’ technology to knock down the responsible gene, and an engineered yeast strain with the gene inserted. Even in initial experiments, thebaine production in yeast increased by more than 20-fold.
Epimeron and Intrexon have patented the gene for yeast-based opiate production.
“The most exciting possibility from this breakthrough work is opening the door to developing new and better opiates,” says Joseph Tucker, CEO of Epimeron.
The team’s research was supported by Intrexon, Epimeron, the National Research Council of Canada’s Industrial Research Assistance Program, Innovate Calgary and the University of Calgary.