Involved in the biosynthesis of clerodane diterpenoids natural products, including salvinorin A with potent agonistic activity on brain kappa-opioid receptors, thus confering hallucinogenic properties (PubMed:30468448). Diterpene synthase that catalyzes the formation of (-)-kolavenyl diphosphate from geranylgeranyl diphosphate (GGPP) as the first reaction in salvinorin A biosynthesis (PubMed:27865008, PubMed:28204567). (2E,6E,10E)-geranylgeranyl diphosphate = (-)-kolavenyl diphosphate Inhibited by high concentrations of magnesium. kcat is 0.88 with geranylgeranyl diphosphate as substrate. Optimum pH is 7.0. Expressed in peltate glandular trichomes of leaves (PubMed:27865008). Highly expressed in the first leaf pair (PubMed:28204567). The Asp-Xaa-Asp-Asp (DXDD) motif is important for the catalytic activity through binding to Mg(2+). Belongs to the terpene synthase family. Tpsc subfamily.