Short-chain dehydrogenase/reductase; part of the gene cluster that mediates the biosynthesis of the tropolone class of fungal maleic anhydrides (PubMed:22508998, PubMed:24863423). The pathway begins with the synthesis of 3-methylorcinaldehyde by the non-reducing polyketide synthase (PKS) tropA (PubMed:22508998). 3-methylorcinaldehyde is the substrate for the FAD-dependent monooxygenase tropB to yield a dearomatized hydroxycyclohexadione (PubMed:22508998, PubMed:24863423). The 2-oxoglutarate-dependent dioxygenase tropC then performs the oxidative ring expansion to provide the first tropolone metabolite stipitaldehyde (PubMed:22508998, PubMed:24863423). Trop D converts stipitaldehyde into stipitacetal which is in turn converted to stipitalide by the short-chain dehydrogenase/reductase tropE (PubMed:24863423). The next steps involve tropF, tropG, tropH, tropI and tropJ to form successive tropolone maleic anhydrides including stipitaldehydic, stipitatonic and stipitatic acids (PubMed:24863423). Secondary metabolite biosynthesis. Belongs to the short-chain dehydrogenases/reductases (SDR) family.