Molecular cloning and characterization of drimenol synthase from valerian plant ( Valeriana officinalis )

Drimenol, a sesquiterpene alcohol, and its derivatives display diverse bio‐activities in nature. However, a drimenol synthase gene has yet to be identified. We identified a new sesquiterpene synthase cDNA ( VoTPS3 ) in valerian plant ( Valeriana officinalis ). Purification and NMR analyses of the VoTPS3‐produced terpene, and characterization of the VoTPS3 enzyme confirmed that VoTPS3 synthesizes (−)‐drimenol. In feeding assays, possible reaction intermediates, farnesol and drimenyl diphosphate, could not be converted to drimenol, suggesting that the intermediate remains tightly bound to VoTPS3 during catalysis. A mechanistic consideration of (−)‐drimenol synthesis suggests that drimenol synthase is likely to use a protonation‐initiated cyclization, which is rare for sesquiterpene synthases. VoTPS3 can be used to produce (−)‐drimenol, from which useful drimane‐type terpenes can be synthesized.