Scheme 1.
Plausible isopimaradiene biosynthesis [81] starting with (E,E,E)-geranylgeranyl diphosphate (GGPP): (E,E,E)-geranylgeranyl diphosphate; CPS: copalyl diphosphate (CPP) synthases; PS: Unknown enzyme; AoCPS-PS, NfCPS-PS, and AfCPS-PS: bifunctional (iso) pimaradiene synthases.