Non-reducing polyketide synthase; part of the gene cluster that mediates the biosynthesis of andrastins, meroterpenoid compounds that exhibit inhibitory activity against ras farnesyltransferase, suggesting that they could be promising leads for antitumor agents (PubMed:28529508). The first step of the pathway is the synthesis of 3,5-dimethylorsellinic acid (DMOA) by the polyketide synthase adrD via condensation of one acetyl-CoA starter unit with 3 malonyl-CoA units and 2 methylations (By similarity). DMAO is then converted to farnesyl-DMAO by the prenyltransferase adrG (By similarity). The methyltransferase adrK catalyzes the methylation of the carboxyl group of farnesyl-DMAO to farnesyl-DMAO methyl ester which is further converted to epoxyfarnesyl-DMAO methyl ester by the FAD-dependent monooxygenase adrH (By similarity). The terpene cyclase adrI then catalyzes the carbon skeletal rearrangement to generate the andrastin E, the first compound in the pathway having the andrastin scaffold, with the tetracyclic ring system (By similarity). The post-cyclization tailoring enzymes adrF, adrE, adrJ, and adrA, are involved in the conversion of andrastin E into andrastin A. The short chain dehydrogenase adrF is responsible for the oxidation of the C-3 a hydroxyl group of andrastin E to yield the corresponding ketone, andrastin D. The ketoreductase adrE stereoselectively reduces the carbonyl moiety to reverse the stereochemistry of the C-3 position to yield andrastin F. The acetyltransferase adrJ is the acetyltransferase that attaches the acetyl group to the C-3 hydroxyl group of andrastin F to yield andrastin C. Finally, the cytochrome P450 monooxygenase adrA catalyzes two sequential oxidation reactions of the C-23 methyl group, to generate the corresponding alcohol andrastin B, and aldehyde andrastin A (By similarity). acetyl-CoA + 3 malonyl-CoA + 2 S-adenosyl-L-methionine = 3,5-dimethylorsellinate + 3 CO2 + 4 CoA + 2 S-adenosyl-L-homocysteine Secondary metabolite biosynthesis; terpenoid biosynthesis. Multidomain protein; including a starter unit:ACP transacylase (SAT) that selects the starter unit; 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 product template (PT) domain that controls the immediate cyclization regioselectivity of the reactive polyketide backbone; a methyltransferase (CMeT) domain that transfers methyl groups to the growing polyketide; and an acyl-carrier protein (ACP) that serves as the tether of the growing and completed polyketide via its phosphopantetheinyl arm. The release of the polyketide chain from the non-reducing polyketide synthase is mediated by the thioesterase (TE) domain localized at the C-ter of the protein. Drastically reduces the production of andrastin A.