Bifunctional terpene synthase; part of the gene cluster that mediates the biosynthesis of the diterpene methyl phomopsenonate (PubMed:19161275, PubMed:28270685). At first, the universal precursor of diterpene, geranylgeranyl diphosphate (GGPP) is provided and is cyclized by the unusual bifunctional terpene synthase PaPS to give phomopsene (PubMed:19161275, PubMed:28270685). The C-terminal prenyltransferase domain of PaPS catalyzes formation of GGPP, whereas the N-terminal terpene cyclase domain catalyzes the cyclization of GGPP to phomopsene (PubMed:19161275, PubMed:28270685). Since the oxidation of a methylgroup to a carboxyl group is frequently catalyzed by a cytochrome P450 monooxygenase, the C-16 methyl group would be oxidized by the cluster-specific cytochrome P450 monooxygenase ORF3 (Probable). Subsequently, oxidation of the allylic position and methylation of the carboxyl group may give methyl phomopsenonate (Probable). Although further study is necessary to identify genes such as a monooxygenase and a methyltransferase, the predicted functions of genes on the cluster are correlated with the structure of methyl phomopsenonate (Probable). (2E,6E)-farnesyl diphosphate + isopentenyl diphosphate = (2E,6E,10E)-geranylgeranyl diphosphate + diphosphate Secondary metabolite biosynthesis; terpenoid biosynthesis. Hexamer. The conserved DDXXD motifs as well as the NSE/DTE motif 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.