Involved in defensive oleoresin formation in conifers in response to insect attack or other injury. Involved in diterpene (C20) olefins biosynthesis. Bifunctional enzyme that catalyzes two sequential cyclizations of geranylgeranyl diphosphate (GGPP) to abietadiene. The copalyl diphosphate (CPP) intermediate diffuses freely between the 2 active sites in the enzyme. (2E,6E,10E)-geranylgeranyl diphosphate = (+)-copalyl diphosphate (+)-copalyl diphosphate = abieta-7,13-diene + diphosphate (+)-copalyl diphosphate = diphosphate + neoabietadiene (+)-copalyl diphosphate = abieta-8(14),12-diene + diphosphate Binds 3 Mg(2+) ions per subunit. Terpene metabolism; oleoresin biosynthesis. Monomer. The Asp-Xaa-Asp-Asp (DXDD) motif is important for the catalytic activity in the class II active site relevant for the cyclization of GGPP. The Asp-Asp-Xaa-Xaa-Asp/Glu (DDXXD/E) motif is important for the catalytic activity in the class I active site, presumably through binding to Mg(2+). Belongs to the terpene synthase family. Tpsd subfamily.