SCIENTISTS have designed a yeast capable of turning sugar into powerful opiate drugs including morphine and, potentially, heroin — without the need to cultivate poppies.
The genetically modified yeast is similar to those used in making wine and beer but instead it can produce class A narcotics.
The researchers say the aim is to make medicinal drugs more efficiently and cheaply than farming poppies — but they acknowledge the discovery could also be used to produce drugs such as heroin via homebrew kits.
Such a discovery could potentially transform the global narcotics trade, moving production of opiates from the poppy fields of Afghanistan, currently producing most of the 440 tons of heroin consumed globally each year, to the back streets of any city.
“We show the functional expression of all known opium poppy genes leading to codeine and morphine synthesis in yeast and demonstrate for the first time that thebaine can be synthesized in S. cerevisiae [yeast],” said the researchers in a paper in PLOS, a journal.
“Thebaine and morphine are the two main opiates extracted from opium poppy latex, meaning that they are the starting precursors for the synthesis of other opioids.” The research, led by Vincent Martin of Concordia University in Canada, says the key aim was the production of benzylisoquinoline alkaloids, a family of 2,500 molecules with a range of medicinal uses including muscle relaxants, tumour suppressants and painkillers. They include opiates such as codeine and morphine — important painkillers that can also be used to make heroin. At the moment poppies are the only commercial source.
Martin and his colleagues wrote: “Efficient production of opiates using microbial platforms could reduce the cost of opiate production.”
Other scientists are also working to make opium poppies redundant.
In a separate paper, in Nature Chemical Biology, Christina Smolke and colleagues at Stanford University, California, said: “Engineered microbial synthesis of plant-derived therapeutic molecules is positioned to supplement or replace drug crop cultivation.
“We demonstrated S. cerevisiae as a host for transforming thebaine to valuable opioids including codeine and morphine.”
Smolke warns that biologists must develop “genetically encoded” safety measures to “secure yeast strains for the legitimate production of drugs with the potential for misuse”.
Synthetic Biology
Whenever journalists, futurists and ethicists come up with Top Ten lists of ways the human race will bring about its own demise, an entry for “synthetic biology” inevitably edges up in the rankings. Pundits love to cite the example of how this technology might let smallpox be turned into an unstoppable weapon by marshaling the capabilities of this emerging technology.
So far, this type of doomsday scenario has come nowhere close. In fact, borrowing an enzyme from one organism and repurposing it for a new use in another—as if one were transferring a part between two used cars—has so far only shown its benign side. Synthetic biology has already demonstrated new ways to make anti-malarial medicine, scents, flavors, industrial chemicals and such.
The honeymoon for any new technology does not last forever. One of the first instances of the possible dark side of synthetic biology just appeared online in Nature Chemical Biology. Researchers from the University of California at Berkeley and Concordia University in Montreal have just reported on a means to coax yeast to make the chemical, reticuline, a critical intermediate step in producing morphine and other opiates.
Combining reticuline with other parts of the manufacturing process, already demoed in separate laboratories, would enable the making of opiates in yeast—no poppies required. All that is needed is to feed spoonfuls of sugar to the engineered microbe. Putting all of this together into an integrated morphine-making machine has yet to be done. But all the steps are now in place. “This sort of metabolic engineering optimization is fairly straightforward,” says George Church, a professor of genetics at Harvard Medical School, and one of the pioneers of synthetic biology. “Once the recipe is published, it becomes very easy to reproduce it—something that many amateur garage labs could do.”
The paper is more than a technical tour de force. The researchers also went to extra lengths to anticipate unavoidable questions about the risks of a home-brew opiate kit. Before going to press, John Dueber of Berkeley and Vincent Martin of Concordia, the lead researchers in the study, contacted two political scientists from MIT and a professor of public health from the University of Alberta, all experts in technology policy, to provide analysis and commentary about ways to ensure the technology does not fall into the wrong hands.
In an accompanying online comment in Nature, Kenneth Oye and Chappell Lawson of MIT and Tania Bubela from the University of Alberta issued a call for establishing a regulatory framework that goes beyond existing rules for anthrax, smallpox and other pathogenic bacteria and viruses. “You really want to control this before it gets out,” Bubela says. “Once the barn door is open and it’s unbolted, it’s a lot harder to control.” To prevent illict use, they advocate measures such as making yeast strains with a DNA watermark that could be identified by law-enforcement.
The yeast could also be engineered so that an additional nutrient has to be added for the production process to proceed. Screening could be instituted for DNA sequences that might be ordered from commercial outfits to engineer opiate-producing yeast. Microbes could be stored in biosecurity facilities and the U.S. Controlled Substance Act could be extended to encompass yeast that produce opium.
The publications will likely lead to prolonged debate about bioengineered narcotics and also force a larger look at synthetic biology in general. Christina Smolke, a Stanford researcher who has also labored on opiate production in yeast, took issue with the idea that a new regulatory scheme should be immediately brought up for consideration. Making opiates from yeast “will require very specialized and highly controlled fermentation conditions, which are not readily accessible to nonspecialists,” she says. “In fact, it is more likely that a person could more easily access morphine by dumping a bunch of poppy seeds in their home brew (or tea).” Smolke agrees that careful discussion of risks and ensuing regulatory issues are needed, but does not see the assertive urgency reflected in the commentary. “This should ideally not be led with a sensationalist, inflammatory approach that is not grounded in accurate representations of the technical capabilities.”
Hank Greely, a bioethicst from Stanford, endorsed the commentary’s call to action, but added that a new technology to manipulate genes—CRISPR/Cas9—may make it relatively easy for a criminal syndicate to engineer an opiate-producing yeast strain. He also thinks that regulators may be slow to give their nod to the new technology. “It seems to me entirely possible that the only uses of this discovery will be illicit,” he says.
The publication, he says, also illustrates the need to revamp the existing regulatory infrastructure to accommodate new technologies that may soon range the gamut from preventing disease transmission to bringing back extinct animals. "We need to think hard about new regulatory systems—national and international—that don't foreclose the potential benefits of engineering life, but that provide some protection against its risks - from environmental damage to new waves of drug abuse."
What drives Dueber and Martin’s research is not the novelty of cranking out opiates in modified beer-making equipment. Feeding in sugar at one end of the pathway and collecting the valued reticuline at the other will enable them to find new ways of making more than just morphine and its cousins. A ready source of reticuline can be used to explore new leads for anti-cancer, antibiotics, among others.
Their research exemplifies a new trend that is advancing biotechnology into the realm of synthetic biology, moving beyond inserting a single gene into an organism and making single proteins. Engineering entire chemical pathways into yeast and other biomanufacturing systems—borrowing molecules from different organisms to facilitate each step of the process—is what inspires researchers whose wish is to harvest the nascent power of synthetic biology.
The Science
Step aside, poppy. Biologists in California and Canada have created strains of yeast that can feast on sugar and make opiates – the key ingredients in pain relievers like morphine.
The new study, published today in the journal Nature Chemical Biology, represents a coup for scientists and drug companies that currently rely on extracting drugs like morphine and codeine directly from poppies and other plants, a process that’s expensive and can yield impurities that cause harmful side-effects. The discovery could mean cheaper medications — where biochemists brew large batches of pure opiates overnight rather than waiting months for poppy fields to grow. It could also have dangerous consequences if it falls into the wrong hands.
“This work is going to enable the production of novel [pain-relieving] analgesics that are safer and less addictive,” said MIT political scientist Kenneth Oye, who co-wrote an accompanying commentary for Nature Chemical Biology about possible regulations and was not involved with the research. “The other part of the equation is if those yeast strains work their way into broad circulation, then you’re talking about fundamental changes in illicit drug production and distribution.”
Yeast could streamline the drug-making process by bypassing plants, which grow slowly and produce only small amounts of chemicals, and move the process instead to a beaker, where scientists could brew larger quantities of the drug.
To envision how researchers moved the opiate-making process from plants to yeast, picture a staircase with 15 steps. Glucose, a sugar compound, sits at the bottom, while the top level is filled with morphine, codeine and other members of a drug family known as benzylisoquinoline alkaloids (BIAs). At each step up, a different enzyme transforms sugar into a new compound, adding to the complexity of the chemical structure.
In the past, scientists relied on yeast for only the final steps, fabricating the opiates from the compounds created at the intermediate steps.
Scientists have known that yeast could also make the early stages of the process more efficient, but they’ve never isolated the right enzyme to make it work. At that stage, a compound is required called L-dopa, which is made by the enzyme tyrosine hydroxlase. Despite years of searching, scientists had never found a version of the tyrosine hydroxylase enzyme in plants, animals or bacteria that could work in yeast. And using yeast in both the early and late stages of the process would simplify the process.
Then in January 2014, William DeLoache — a biologist and graduate student at the University of California, Berkeley and lead author of the study – devised a way to fill the L-dopa void. At the time, DeLoache was working with the plant Mirabalis jalapa – the four o’clock flower, whose petals contain a protein that converts L-dopa into a highly fluorescent and colorful pigment, ostensibly to attract insect pollinators.
“William saw that this protein could serve as a means for detecting when L-dopa is present in yeast cells,” said John Dueber, a synthetic biologist and DeLoache’s thesis mentor at UC Berkeley.
For today’s study, DeLoache took the four o’clock flower protein and genetically added it to a yeast strain, creating a biosensor for L-dopa, a way for scientists to identify its presence.
“To me, the heart of the study is the sensor that they developed,” said biochemist Pamela Peralta-Yahya of the Georgia Institute of Technology. And that sensor, she explained, allowed them to identify the enzyme they needed to fill the gap in opiate synthesis. On a hunch, they spotted the enzyme in sugar beets.
“It’s known that L-dopa is an intermediate in the pathway that produces the pigment responsible for the beet’s violet color,” Dueber said. “So [DeLoache] took a guess at the beet’s gene [for tyrosine hydroxylase], inserted it into the biosensor yeast strain, and the cells glowed.”
Colorful yeast cells were a neat trick, but their real mission was alkaloid production. So they took the glowing yeast and removed the protein that turned L-dopa into a bright dye. They tried replacing this pigment with a string of enzymes that could yield opiates.
At first, they struggled, so they reached out to co-author and microbial engineer Vincent Martin of Concordia University in Montreal.
“Vincent’s lab had demonstrated that they could execute these [first steps] in yeast to synthesize an anti-cancer drug,” Dueber said.
In the end, by collaborating with Martin’s team, the researchers built a yeast strain that could take glucose and pump out (S)-reticuline, the chemical predecessor for the entire family of benzylisoquinoline alkaloids – whose 2,500 members includes the painkillers morphine and codeine, the antibiotics sanguinarine and berberine, the muscle relaxant papaverine and the cough suppressant noscapine.
The final brewer’s yeast produces very low amounts of alkaloid, and right now, it is highly unlikely that a drug trafficker possesses the technology or scientists to recreate this study, Dueber said. Even if they did, they would get nearly undetectable amounts of opium.
But more potent strains are inevitable, he added.
“Whereas a year ago, I thought that putting all of these enzymes together into a single yeast cell might take a decade, now we’re thinking that high-producing opiate strains might be completed in two to three years,” Dueber said. “The regulations need to be reconsidered because they’re not currently written for microbial factories that produce a controlled substance.”
Worried by this accelerated timeline, the team took the initiative to contact Oye and other policy experts, so the latter could start an independent discussion on how to regulate illicit use, while still maintaining the ability to make alkaloids that could lower the cost of medicines or even create new, safer opiate drugs.
The fact that these scientists were even willing to talk about the risks at such an early stage was something that I hadn’t seen before, Oye said. Stricter regulatory policy might stifle the researcher’s ability to do future work.
Oye’s op-ed calls for licenses for producers and security systems to prevent misuse or theft. In addition, they recommend that DNA tags be added to opiate yeast, so if law enforcement confiscates a stolen strain, then they can trace the original source.
“You want to make these strains less appealing for illicit use, and at the same time, you want to make release of the strains into the general public far less likely,” Oye said. “We’ve taken an unusual step by contacting two regulatory authorities — the International Narcotics Control Board and International Experts Group on Biosafety and Biosecurity Regulation — to get this on the agenda as soon as possible.”
“The debate and discussion needs to take place before people fully realize the concept,” he said.