Pot has been in the news lately. Jeb Bush publically apologized to his mother for “smoking marijuana” in college, and pending state legislature may make Ohio the fifth state to legalize recreational marijuana use. A more significant announcement regarding the drug was made this past May when researchers artificially synthesized THC, the most potent “active ingredient” in marijuana, by engineering a strain of yeast. This new plant-free production of THC and its derivatives could eliminate a lot of red tape for researchers who are currently unable to study these molecules due to state and federal restrictions on growing Cannabis plants.
The earliest recorded uses of yeast as an important tool in manufacturing date back some 5,000 years to the Ancient Egyptians. Ancient innovators, albeit unknowingly, applied the naturally occurring life-processes of yeast to various industrial problems, just as we do when we add baker’s yeast to dough. But current-day scientists can do much more with yeast than the Egyptians ever could because they are not limited by the chemistry that naturally occurs within an organism. Through a process called heterologous gene expression, scientists today can expand the function of a particular organism by expanding the organism’s genetic code.
The word heterologous comes from the Greek hetero, which means “different,” and the Greek logos, meaning “logic.” To heterologously express a gene is to remove it from the organism in which it is naturally found and to insert it into another organism. Researchers at TU Dortmund University in Germany heterologously expressed a gene from the Cannabis plant in Pichia pastoris, a species of yeast commonly used in research. Once integrated into the yeast’s genetic code, the gene manufactured an enzyme, a protein that can helps chemical reactions proceed. The researchers then fed the yeast a specific molecule that this enzyme chemically transformed into THC.
The use of genetically modified microorganisms in the production of important compounds is not new. Since the 1980s, the insulin taken by millions of Americans has been harvested from E. coli, which does not naturally produce the hormone. Still, genetically modifying an organism is not simply a matter of molecular “copy and paste.” The environment inside yeast cells differs substantially from the environment inside Cannabis cells. In order to better simulate the conditions in which the gene and its associate protein occur in nature, several other genetic modifications had to be made to the yeast.
The researchers stated that while this innovation represents an important step towards the total biological synthesis of THC and its derivatives, there is still significant work left to be done. Currently, the precursors fed to the modified yeast must first be chemically synthesized. They aim to further modify their mutants such that THC may be produced from basic sugar molecules alone.
If the total biological synthesis of THC is achieved, the ramifications for researchers, physicians, and patients suffering from chronic illness will be substantial. Current restrictions on the use of Cannabis plants in chemical and biological research have made it difficult to study the molecules produced by the plant in exquisite detail. These restrictions have also hindered the study of the effectiveness of THC as a therapeutic drug, making it difficult to discern when it is or is not appropriate for doctors to issue prescriptions. And for those patients who would benefit from treatment with THC, total biosynthesis of the compound promises to increase availability and decrease costs.
Zach Gardner is a junior in Ezra Stiles College. Contact him at firstname.lastname@example.org.
(Featured image from Wiki commons.)