A cDNA clone for 3-carene synthase from Salvia stenophylla

The essential oil of Salvia stenophylla contains (+)-3-carene as the principal monoterpene component. Using an enriched cDNA library prepared from mRNA isolated from S. stenophylla peltate glandular trichomes, and a homology-based cloning strategy, a full-length cDNA was isolated that encoded a preprotein of 69.7 kDa which resembled a monoterpene synthase in sequence. Heterologous expression of the gene in Escherichia coli provided a soluble recombinant enzyme capable of catalyzing the divalent metal ion-dependent conversion of geranyl diphosphate to (+)-3-carene and to lesser amounts of limonene, myrcene, 4-carene and beta-phellandrene. This multiple-product synthase is responsible for the production of all of the essential oil monoterpenes of S. stenophylla.