Scientists have come closer in creating palliative medicines using yeast cells instead of poppy plants.
For centuries, poppy plants had been grown to provide opium, the compound from which morphine and other important medicines such as oxycodone are derived, but now bioengineers at Stanford have hacked the DNA of yeast, reprograming these simple cells to make opioid-based medicines via a sophisticated extension of the basic brewing process that makes beer.
The Stanford team had spent a decade genetically engineering yeast cells to reproduce the biochemistry of poppies, and in the new report, they detail how added five genes from two different organisms to yeast cells. Three of these genes came from the poppy itself, and the others from a bacterium that lives on poppy plant stalks.
Morphine is one of three principal pain killers derived from opium. As a class they are called opiates. The other two important opiates are codeine, which has been used as a cough remedy, and thebaine, which is further refined by chemical processes to create higher-value therapeutics such as oxycodone and hydrocodone, better known by brand names such as OxyContin and Vicodin, respectively.
Led by Christina Smolke, the team carefully reprogrammed the yeast genome; the master instruction set that tells every organism how to live, to behave like a poppy when it comes to making opiates.
The process involved more than simply adding new genes into yeast. Opioid molecules are complex three-dimensional objects. In nature they are made in specific regions inside the poppy.
Since yeast cells do not have these complex structures and tissues, the Stanford team had to recreate the equivalent of poppy-like 'chemical neighborhoods' inside their bioengineered yeast cells.It took about 17 separate chemical steps to make the opioid compounds used in pills. Some of these steps occurred naturally in poppies and the remaining via synthetic chemical processes in factories.
The study is published in Nature Chemical Biology.
