Alpha-ketoglutarate-dependent dioxygenase; part of the gene cluster that mediates the biosynthesis of betaestacins (PubMed:29185768, Ref.2). The bifunctional terpene synthase btcA converts isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) into the sesterterpene betaestacin I (PubMed:29185768, Ref.2). The C-terminal prenyltransferase (PT) domain of btcA catalyzes formation of GFPP, whereas the N-terminal terpene cyclase (TC) domain catalyzes the cyclization of GFPP into betaestacin I (PubMed:29185768, Ref.2). The cytochrome P450 monooxygenase btcB is then responsible for the six-step oxidation of betaestacin I to yield betaestacin II (Ref.2). The roles of the cytochrome P450 monooxygenase btcC and the alpha-ketoglutarate-dependent dioxygenase btcD have not been identified yet (Probable). Binds 1 Fe(2+) ion per subunit. Secondary metabolite biosynthesis; terpenoid biosynthesis. Belongs to the TfdA dioxygenase family.