Oxidosqualene cyclase involved in the production of shionone, a triterpenoid with a rare 6/6/6/6 tetracyclic skeleton and a C-3 carbonyl carbon. Produces also small amounts of beta-amyrin, friedelin, dammara-20,24-dienol, and 4-epishionone. (S)-2,3-epoxysqualene = shionone Expressed in stems, leaves and flowers. Lower expression in roots, stolons, rhizomes and radical leaves. Belongs to the terpene cyclase/mutase family.