Bifunctional terpene synthase; part of the gene cluster that mediates the biosynthesis of aspergiltriene A, aspergildienes A-D and aspergilols A-D (PubMed:33480256). The bifunctional terpene synthase AuAS converts isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) into sesterterpenes (PubMed:33480256). The C-terminal prenyltransferase (PT) domain of AuAS catalyzes formation of GFPP, whereas the N-terminal terpene cyclase (TC) domain catalyzes the cyclization of GFPP into 5 distinct sesterterpenes: aspergiltriene A, aspergildiene A, aspergildiene B, aspergildiene C and aspergildiene D (PubMed:33480256). The cytochrome P450 monooxygenase AP450 then hydroxylates the aspergildienes A, B, C and D to yield the corresponding sesterterpene alcohols, aspergilols A-D (PubMed:33480256). (2E,6E)-farnesyl diphosphate + isopentenyl diphosphate = (2E,6E,10E)-geranylgeranyl diphosphate + diphosphate (2E,6E,10E)-geranylgeranyl diphosphate + isopentenyl diphosphate = (2E,6E,10E,14E)-geranylfarnesyl 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+). Aspergilol A shows a weak cytotoxicity toward MCF-7, MDA-MB231, and HepG2 cancer cells lines, with an IC(50) value ranging from 21.21 to 48.76 uM; whereas aspergilol B only shows a weak cytotoxicity against MCF-7 cells, with an IC(50) value of 27.41 uM (PubMed:33480256). None of the aspergilols have antifungal or antibacterial activities (PubMed:33480256). In the N-terminal section; belongs to the terpene synthase family. In the C-terminal section; belongs to the FPP/GGPP synthase family.