Trans-enoyl reductase; part of the gene cluster that produces the tetronate natural products trihazones (PubMed:33570538). The PKS-NRPS synthetase thnA with the help of the trans-enoyl reductase thnE are responsible for the synthesis of the carboxylmethyl containing trihazone A (PubMed:33570538). The PKS portion of thnA synthesizes beta-keto-triene chain from one acetyl-CoA and 6 equivalents of malonyl-CoA, in collaboration with thnE, which selectively reduces the enoyl intermediate during the first and fourth iteration of the PKS (PubMed:33570538). The NRPS domain selects and activates malate, of which the alpha-hydroxyl group attacks the completed polyketide acyl-S-ACP chain to form the ester product (PubMed:33570538). Intramolecular Dieckmann cyclization catalyzed by the terminal reductase domain releases the product as trihazone A from the PKS-NPRS (PubMed:33570538). The pathway begins with the formation of trihazone A by the hybrid PKS-NRPS synthetase thnA and the trans-enoyl reductase thnE. Trihazone A is further decarboxylated by the 2-oxoglutarate-dependent dioxygenase thnC to produce trihazone D. The function of the FAD-dependent monooxygenase thnD has still to be identified (PubMed:33570538). Secondary metabolite biosynthesis. Monomer. Belongs to the zinc-containing alcohol dehydrogenase family.