Highly reducing polyketide synthase; part of the gene cluster that mediates the biosynthesis of the meroterpenoids nectripenoids A and B, as well as cochliquninone D and isocochliquninone E (PubMed:29797385). The pathway probably begins with the HR-PKS ntnH that catalyzes two chain-extension steps to form a reduced triketide, which then primes the SAT domain in the NR-PKS ntnG to initiate three more cycles of extension to give a linear hexaketide corresponding to the polyketide part of nectripenoids (Probable). The FAD-dependent monooxygenase ntnJ then performs an oxidative decarboxylation at C11 of the ntnH/ntnG product, via an electrophilic aromatic hydroxylation with concomitant ipso-decarboxylation (Probable). The membrane-bound polyprenyl transferase ntnF then introduces a farnesyl group before the FAD-dependent monooxygenase ntnK functions as the first epoxidase on terminal C12'-C13' olefin, followed by a second epoxidation on C7'-C8' catalyzed by ntnA (Probable). The terpene cyclase/mutase ntnI then initiates the sequential tricyclic ring formation through protonation of the terminal epoxide and catalyzes the regioselective and stereoselective 6/6/6-tricyclic ring formation (Probable). The cytochrome P450 monooxygenase ntnM may then hydroxylate C1' (Probable). Secondary metabolite biosynthesis; terpenoid biosynthesis. Multidomain protein; including a ketosynthase (KS) that catalyzes repeated decarboxylative condensation to elongate the polyketide backbone; a malonyl-CoA:ACP transacylase (MAT) that selects and transfers the extender unit malonyl-CoA; a dehydratase (DH) domain that reduces hydroxyl groups to enoyl groups; a methyltransferase (CMeT) domain responsible for the incorporation of methyl groups; an enoylreductase (ER) domain that reduces enoyl groups to alkyl group; a ketoreductase (KR) domain that catalyzes beta-ketoreduction steps; and an acyl-carrier protein (ACP) that serves as the tether of the growing and completed polyketide via its phosphopantetheinyl arm. The lack of conserved catalytic residues in the ER domain supports the fact that nectripenoids retain an alkene at C2-C3.