Function
Glutathione S-transferase; part of the gene cluster that mediates the biosynthesis of pseurotin A, a competitive inhibitor of chitin synthase and an inducer of nerve-cell proliferation (PubMed:24082142, PubMed:24939566). The PKS-NRPS hybrid synthetase psoA is responsible for the biosynthesis of azaspirene, one of the first intermediates having the 1-oxa-7-azaspiro[4,4]-non-2-ene-4,6-dione core of pseurotin, via condensation of one acetyl-CoA, 4 malonyl-CoA, and a L-phenylalanine molecule (PubMed:24082142, PubMed:24939566). The dual-functional monooxygenase/methyltransferase psoF seems to be involved in the addition of the C3 methyl group onto the pseurotin scaffold (PubMed:24939566). Azaspirene is then converted to synerazol through 4 steps including oxidation of C17 by the cytochrome P450 monooxygenase psoD, O-methylation of the hydroxy group of C8 by the methyltransferase psoC, and the trans-to-cis isomerization of the C13 olefin by the glutathione S-transferase psoE (PubMed:24939566, PubMed:27072782). The fourth step of synerazol production is performed by the dual-functional monooxygenase/methyltransferase psoF which seems to catalyze the epoxidation of the intermediate deepoxy-synerazol (PubMed:24939566). Synerazol can be attacked by a water molecule nonenzymatically at two different positions to yield two diol products, pseurotin A and pseurotin D (PubMed:24939566).