Function
Carboxylesterase; part of the gene cluster that mediates the biosynthesis of patulin, an acetate-derived tetraketide mycotoxin produced by several fungal species that shows antimicrobial properties against several bacteria (PubMed:25120234, PubMed:30100914). The pathway begins with the synthesis of 6-methylsalicylic acid by the polyketide synthase (PKS) patK via condensation of acetate and malonate units. PatG then catalyzes the decarboxylation of 6-methylsalicylic acid to yield m-cresol. The cytochrome P450 monooxygenase patH then converts m-cresol to m-hydroxybenzyl alcohol, which is further converted to gentisyl alcohol by the cytochrome P450 monooxygenase patI. The conversion of gentisyl alcohol to two-ring compound neopatulin remains a matter of speculation, but it involves at least two intermediates, isoepoxydon and phyllostin. PatN catalyzes the transformation of isoepoxydon into phyllostin. The last part of the biosynthetic pathway involves the conversion of neopatulin to ascladiol followed by the transformation of the latter into patulin (By similarity).
Sequence
MQIINWASLLLVTWETVVAAELPIVDLGYQRHQAIGFNSTGRYYQFSNVRYAEPPLGPLRFSLPVSPRNRSHEVVNGKGLGNICPQSQACWFNVQGDFVSAVTAGSTFNFTAAYDQVYQQDECTKPRPVADQNPLESEDCLFLDVYVPEKVISKRRDGNGKSNPGAPVLVYFQDGAYVSGSKSDQNPSGLIATSREDGSTGIIYVGVNYRLGVFGWLSGQKFQSEGGLPNAGLYDERLALEWVQRHITKFGGDPSRVTVMGVSAGGGSITMQLTAYGRAIRPPFAQIIAQSPAWEPGTKTPAIEDDLLDSFLTLLNVSSLEEARRLPSQALLDANYELVASRPYGSGVFGPAIDGSFVPDSPKRLLLERKVDPSVRILTSYTANEGFMLAPANVTDDATFNRYVDVLLRGANASVRAHTSRVLYPPIFNGSWPYHSQHERANLLWSEVSTTCNTRYLHQAVATPGYAIEYAVKPAMHLSDTSSVFYNGQGSSSSLNATIAQLMQRQIVQFVKTGNPNVKGDPHVPLYHGQAHVLSLGDNGVRVEPALTNTDRCTYWQQVEF