pxr2

Aristolochene synthase prx2

342 amino acids

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). 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:24239699). Following the formation of aristolochene, the non-oxygenated aristolochene is converted to the trioxygenated intermediate eremofortin B (PubMed:24239699). This conversion appears to involve three enzymes, a hydroxysterol oxidase-like enzyme prx7, a 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 a P450 monooxygenase (prx8 or prx9) that introduces the epoxide at the double bond between carbons 1 and 2 (PubMed:24239699). 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 (PubMed:24239699). The second epoxidation may be performed by the second P450 monooxygenase in the cluster (prx9), although the substrate specificity of these two P450 enzymes cannot be predicted (PubMed:24239699). The acetylation step is likely performed by the O-acetyltransferase encoded by prx11, the only acetyl transferase in the entire cluster (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:24239699). The primary alcohol formed by this reaction at C-12 is finally oxidized by the short-chain alcohol dehydrogenase prx4 that forms PR-toxin (PubMed:24239699).

Belongs to the terpene synthase family.

39.153 kDa

MATLTETITSLAQPFVHLEDTINSPPVKETIRPRNDTTITPPPTQWSYLCHPRVKEVQDEVDGYFLENWKFPSFKAVRTFLGAKFSEVTCLYFPLALDDRIHFACRLLTVLFLIDDVLEHMSFADGEAYNNRLIPISRGDVLPDRTKPEEFILYDLWESMRAHDAELANEVLEPTFVFMRAQTDRARLTIHELGHYLEYREKDVGKALLSALMRFSMGLRFSADELQGMKALEANCAKQLSVVNDIYSYDKEEEASRTGHKEGAFLCSAVKVLAEESKLGIPATKRVLWSMTREWETVHDEIVAEKIASPDGCSEAAKAYMKGLEYQMSGNEQWSKTTRRYN