Monofunctional diterpene synthase converting geranylgeranyl diphosphate to copalyl diphosphate. (2E,6E,10E)-geranylgeranyl diphosphate = (+)-copalyl diphosphate Secondary metabolite biosynthesis; terpenoid biosynthesis. The Asp-Xaa-Asp-Asp (DXDD) motif is important for the catalytic activity, presumably through binding to Mg(2+). S.moellendorffii contains two distinct types of functional terpene synthases (TPS) genes, the typical seed plants TPS genes (SmTPSs) and the microbial type TPS genes (SmMTPSLs). Belongs to the terpene synthase family.