Oxidoreductase; part of the gene cluster that mediates the biosynthesis of viridicatumtoxin, a tetracycline-like fungal meroterpenoid with a unique, fused spirobicyclic ring system (PubMed:20534346). The first step of the pathway is the production of the malonamoyl-CoA starter unit for the polyketide synthase vrtA (PubMed:20534346). The aldolase vrtJ may be involved in the synthesis of the malonamate substrate for malonamoyl-CoA synthetase vrtB (PubMed:20534346). The polyketide synthase vrtA then may utilize the malonamoyl-CoA starter unit, followed by sequential condensation of eight malonyl-CoA units to form the polyketide backbone (PubMed:20534346). The cyclization of the last ring could be mediated by the lactamase-like protein vrtG (PubMed:20534346). The proposed post-PKS tailoring steps are an hydroxylation at C5 catalyzed the cytochrome P450 monooxygenase vrtE, a hydroxylation at C12a catalyzed by VrtH and/or VrtI, and an O-methylation by the O-methyltransferase vrtF (PubMed:20534346, PubMed:24161266). VrtC is then proposed to catalyze the transfer of a geranyl group synthesized by vrtD to the aromatic C ring of the tetracyclic polyketide intermediate of viridicatumtoxin to yield previridicatumtoxin (PubMed:20534346). Finally, the cytochrome P450 monooxygenase vrtK catalyzes the spirocyclization of the geranyl moiety of previridicatumtoxin to afford viridicatumtoxin (PubMed:24161266). Secondary metabolite biosynthesis; terpenoid biosynthesis. Viridicatumtoxin and its derivative, viridicatumtoxin B, exhibit anti-methicillin-resistant Staphylococcus aureus (anti-MRSA) activity (PubMed:19168978). Moreover, viridicatumtoxin and a C2 acetyl analog, spirohexaline, have been demonstrated to inhibit bacterial undecaprenyl diphosphate synthase, a potential new target for antibiotic development (PubMed:27049441). Belongs to the iron/ascorbate-dependent oxidoreductase family.