Involved in the biosynthesis of ent-kaurene diterpenoids natural products such as oridonin, miltiradiene, eriocalyxin B and nezukol, known to exhibit antitumor, anti-inflammatory and antibacterial activities, and in the production of gibberellins phytohormones (PubMed:22284743). Catalyzes the conversion of (2E,6E,10E)-geranylgeranyl diphosphate (GGPP) to ent-copalyl diphosphate (ent-CPP) (PubMed:22284743). (2E,6E,10E)-geranylgeranyl diphosphate = ent-copalyl diphosphate Plant hormone biosynthesis; gibberellin biosynthesis. Secondary metabolite biosynthesis; terpenoid biosynthesis. Expressed in germinating seeds and leaves. Accumulates in germinating seeds as well as in leaves. The Asp-Xaa-Asp-Asp (DXDD) motif is important for the catalytic activity, presumably through binding to Mg(2+). Belongs to the terpene synthase family. Tpsc subfamily.