Bifunctional terpene synthase that possesses both prenyltransferase and type II terpene cyclase activity, converting isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) into geranylgeranyl diphosphate (GGPP) and further converting GGPP into copalyl diphosphate, respectively. (2E,6E)-farnesyl diphosphate + isopentenyl diphosphate = (2E,6E,10E)-geranylgeranyl diphosphate + diphosphate (2E,6E,10E)-geranylgeranyl diphosphate = (+)-copalyl diphosphate Binds 4 Mg(2+) ions per subunit. Homohexamer. The bifunctional copalyl diphosphate synthase is composed of an N-terminal type II terpene cyclase (TC) catalytic domain and a C-terminal prenyltransferase (PT) catalytic domain which are separated by a linker region. The conserved DXDD and DDXXD motifs are important for the catalytic activity, presumably through binding to Mg(2+). In the N-terminal section; belongs to the terpene synthase family. In the C-terminal section; belongs to the FPP/GGPP synthase family.