Involved in the biosynthesis of cannabinoids-related terpenophenolic natural products, which have pharmacological activity (PubMed:18323613, PubMed:19454282, PubMed:19581347, PubMed:22802619). Polyketide synthase responsible for olivetol biosynthesis, from a C(12)-polyketide, probably 3,5,7-trioxododecanoyl-CoA (PubMed:19454282, Ref.3). Catalyzes the first step in the cannabinoids biosynthetic pathway. The preferred substrate is hexanoyl-CoA, but accepts also CoA esters with C4 to C8 aliphatic side chains (PubMed:19454282). When using malonyl-CoA and hexanoyl-CoA as substrates, produces undetermined compounds distinct form olivetol or olivetolic acid (PubMed:19581347) that could be hexanoyl triacetic acid lactone (HTAL) (PubMed:18323613) and pentyl diacetic acid lactone (PDAL) (PubMed:22802619). Produces olivetolic acid when acting in concert with olivetolic acid cyclase (OAC). 3 H(+) + hexanoyl-CoA + 3 malonyl-CoA = 3,5,7-trioxododecanoyl-CoA + 3 CO2 + 3 CoA 3,5,7-trioxododecanoyl-CoA = CO2 + CoA + olivetol kcat is 2.96 min(-1) with hexanoyl-CoA as substrate (PubMed:19454282). kcat is 0.719 min(-1) with butyryl-CoA as substrate (PubMed:19454282). kcat is 0.585 min(-1) with isovaleryl-CoA as substrate (PubMed:19454282). kcat is 0.525 min(-1) with octanoyl-CoA as substrate (PubMed:19454282). Secondary metabolite biosynthesis; terpenoid biosynthesis. Expressed in bracts, flowers and young leaves. Not detected in mature leaves, roots and stems. Expressed in glandular trichomes. Several isoforms exist due to polymorphism. Belongs to the thiolase-like superfamily. Chalcone/stilbene synthases family.