Aristolochene synthase

UniProtKB accession:  Q03471

Grouped By:  Matching UniProtKB accession

UniProtKB description:  Aristolochene synthase; part of the gene cluster that mediates the biosynthesis of PR-toxin, a bicyclic sesquiterpene belonging to the eremophilane class and acting as a mycotoxin (PubMed:24239699, PubMed:27921136). The first step of the pathway is catalyzed by the aristolochene synthase which performs the cyclization of trans,trans-farnesyl diphosphate (FPP) to the bicyclic sesquiterpene aristolochene (PubMed:15186158, PubMed:24239699, PubMed:8440737). Following the formation of aristolochene, the non-oxygenated aristolochene is converted to the trioxygenated intermediate eremofortin B, via 7-epi-neopetasone (PubMed:24239699, PubMed:26274339). This conversion appears to involve three enzymes, a hydroxysterol oxidase-like enzyme, the quinone-oxidase prx3 that forms the quinone-type-structure in the bicyclic nucleus of aristolochene with the C8-oxo group and the C-3 hydroxyl group, and the P450 monooxygenase ORF6 that introduces the epoxide at the double bond between carbons 1 and 2 (PubMed:24239699, PubMed:27921136). No monoxy or dioxy-intermediates have been reported to be released to the broth, so these three early oxidative reactions may be coupled together (PubMed:24239699). Eremofortin B is further oxidized by another P450 monooxygenase, that introduces a second epoxide between carbons 7 and 11 prior to acetylation to eremofortin A by the acetyltransferase ORF8 (PubMed:16345540, PubMed:24239699, PubMed:27921136). The second epoxidation may be performed by a second P450 monooxygenase (PubMed:24239699). After the acetylation step, the conversion of eremofortin A to eremofortin C and then to PR-toxin requires only two enzymes (PubMed:24239699). First the conversion of eremofortin A to eremofortin C proceeds by oxidation of the side chain of the molecule at C-12 and is catalyzed by the short-chain oxidoreductase prx1 (PubMed:16345540, PubMed:24239699). The cytochrome P450 monooxygenase ORF5 also plays a role in this step (PubMed:27921136). The primary alcohol formed at C-12 is finally oxidized by the short-chain alcohol dehydrogenase prx4 that forms PR-toxin (PubMed:16345540, PubMed:24239699).