Trans-enoyl reductase; part of the gene cluster that mediates the biosynthesis of HIV-1 integrase inhibitor equisetin and of fusarisetin A, both trans-fused decalin-containing tetramic acids showing also antimicrobial activity (PubMed:25770422). The PKS module of fsa1 together with the enoylreductase fsa3 catalyze the formation of the polyketide unit which is then conjugated to L-serine by the condensation domain of the fsa1 NRPS module (PubMed:25770422). Activity of the Dieckmann cyclase domain (RED) results in release of the Dieckmann product intermediate (PubMed:25770422). Diels-Alderase fsa2 is involved in endo-selective Diels-Alder cycloaddition to form the decalin ring, leading to the production of N-desmethylequisetin also called trichosetin (PubMed:25770422, PubMed:28401214, PubMed:29972614, PubMed:34121297). Subsequent N-methylation is carried out by fsa4 to give equisetin (PubMed:25770422). The enzymatic gene responsible for the conversion of equisetin to fusarisetin A has not been identified yet and is probably located outside of the fsa cluster (PubMed:28401214). acetyl-CoA + ATP + 11 H(+) + L-serine + 7 malonyl-CoA + 8 NADPH + 2 S-adenosyl-L-methionine = (5S)-3-[(2E,6R,8E,10E,12E)-2,6-dimethyltetradeca-2,8,10,12-tetraenoyl]-5-(hydroxymethyl)pyrrolidine-2,4-dione + AMP + 7 CO2 + 8 CoA + diphosphate + 6 H2O + 8 NADP(+) + 2 S-adenosyl-L-homocysteine Mycotoxin biosynthesis. Monomer. Results in the loss of production of equisetin and fusarisetin A (PubMed:25770422). Belongs to the zinc-containing alcohol dehydrogenase family.