Δ9-Tetrahydrocannabinolic acid synthase: The application of a plant secondary metabolite enzyme in biocatalytic chemical synthesis

Δ9-Tetrahydrocannabinolic acid synthase (THCAS) from the secondary metabolism of Cannabis sativa L. catalyzes the oxidative formation of an intramolecular CC bond in cannabigerolic acid (CBGA) to synthesize Δ9-tetrahydrocannabinolic acid (THCA), which is the direct precursor of Δ9-tetrahydrocannabinol (Δ9-THC). Aiming on a biotechnological production of cannabinoids, we investigated the potential of the heterologously produced plant oxidase in a cell-free system on preparative scale. THCAS was characterized in an aqueous/organic two-liquid phase setup in order to solubilize the hydrophobic substrate and to allow in situ product removal. Compared to the single phase aqueous setup the specific activity decreased by a factor of approximately 2 pointing to a substrate limitation of CBGA in the two-liquid phase system. However, the specific activity remained stable for at least 3 h illustrating the benefit of the two-liquid phase setup. In a repeated-batch setup, THCAS showed only a minor loss of specific activity in the third batch pointing to a high intrinsic stability and high solvent tolerance of the enzyme. Maximal space-time-yields of 0.121 g L−1 h−1 were reached proving the two-liquid phase concept suitable for biotechnological production of cannabinoids.