The identification of tetrahydrocannabinolic acid synthase in the non-aqueous secretions of the storage cavities from Cannabis sativa glandular trichomes

Cannabis sativa is an important herbaceous species cultivated since ancient times due to its unique medical and recreational properties, but also as a source of valuable seed oil and high quality fibre. Among numerous phytochemicals synthesized in this herb, cannabinoids represent the unique class of secondary metabolites, which largely contribute to the pharmacological properties of this species. More than 100 cannabinoids have been described in the literature, but Δ⁹-tetrahydrocannabinolic acid (THCA), cannabidiolic acid (CBDA) and cannabichromenic acid (CBCA) are present in the largest quantities in this plant. Cannabinoids are synthesized in glandular trichomes present mainly on female flowers and their main reservoirs are storage cavities of these hair-like structures [1].

Tetrahydrocannabinolic acid synthase catalyzes the unique oxidative cyclization of cannabigerolic acid (CBGA) into THCA, which is a direct precursor of the mind-affecting compound – Δ⁹-tetrahydrocannabinol (THC). Thus, it is considered to be a key enzyme controlling the psychoactive properties of C. sativa. In previous research it was suggested that THCA synthase is secreted into the storage cavities of glandular trichomes, where it might also synthesize the final product – THCA [2]. However, no direct evidence on protein level was presented.

To examine the putative extracellular location of THCA synthase, the storage cavity secretions from C. sativa trichomes were obtained and submitted for proteomic analysis. By using mass spectrometry we were able to identify the THCA synthase in the non-aqueous content of the storage cavities from C. sativa glandular trichomes.

[1] Andre CM, Hausman J-F, Guerriero G. Front. Plant Sci. 2016; 7:19

[2] Sirikantaramas S, Taura F, Tanaka Y, Ishikawa Y, Morimoto S, Shoyama Y. Plant Cell Physiol. 2005; 46, 1578 – 1582