A recent paper published in the Proceedings of the National Academy of Sciences of the United States of America (affectionately known as PNAS) illustrates how some of this research is carried out.
To produce THC, cannabis employs a number of differenet enymes which work in a linear series simplified below:
hexanoyl-CoA + malonylCoA --> OA --> CBGA --> THCA --> THC
Each of the arrows is a different enzyme. A big challenge in understanding how cannabis makes THC (and maybe to be able to make it artificially) is identifying each of the enzymes. As the biochemistry behind this pathway is very complex, this has not been a simple matter.
|trichomes on a Cannabis sativa leaf|
When they put this gene in yeast, the yeast started making OA. Just think of the possibilities for beer if they wold add the genes for the arrows...