Dammaradiene synthase, a squalene cyclase, from Dryopteris crassirhizoma Nakai

A cDNA DCD was cloned from Dryopteris crassirhizoma by RT-PCR. By functional expression in yeast, DCD was found to encode a dammaradiene synthase which converts squalene (5) to dammara-18(28),21-diene (6). Compound (6) was isolated from leaflets of D. crassirhizoma, which have not been reported in this fern.