Production of Δ¹-tetrahydrocannabinolic acid by the biosynthetic enzyme secreted from transgenic Pichia pastoris

Δ¹-Tetrahydrocannabinolic acid (THCA) synthase is the enzyme that catalyzes the oxidative cyclization of cannabigerolic acid into THCA, the acidic precursor of Δ¹-tetrahydrocannabinol. We developed a novel expression system for THCA synthase using a methylotrophic yeast Pichia pastoris as a host. Under optimized conditions, the transgenic P. pastoris secreted ∼1.32 nkat/l of THCA synthase activity, and the culture medium, from which the cells were removed, effectively synthesized THCA from cannabigerolic acid with a ∼98% conversion rate. The secreted THCA synthase was readily purified to homogeneity. Interestingly, endoglycosidase treatment afforded a deglycosylated THCA synthase with more catalytic activity than that of the glycosylated form. The non-glycosylated THCA synthase should be suitable for structure-function studies because it displayed much more activity than the previously reported native enzyme from Cannabis sativa as well as the recombinant enzyme from insect cell cultures.