Function
Non-reducing polyketide synthase; part of the gene cluster that mediates the biosynthesis of the bicoumarin kotanin (PubMed:22945023, PubMed:26389790). The non-reducing polyketide synthase ktnS first catalyzes the formation of the pentaketidic 4,7-dihydroxy-5-methylcoumarin from acetyl coenzyme A and 4 malonyl coenzyme A molecules (PubMed:17315249, PubMed:22945023). Further O-methylation by ktnB leads to the formation of 7-demethylsiderin (PubMed:17315249, PubMed:22945023, PubMed:26389790). Then, an oxidative phenol coupling catalyzed by the cytochrome P450 monooxygenase ktnC forms the 8,8'-dimer P-orlandin via dimerization the monomeric precursor, 7-demethylsiderin (PubMed:26389790). P-orlandin is subsequently O-methylated in a stepwise fashion to demethylkotanin and kotanin (PubMed:22945023). The function of ktnA within the pathway has not been determined yet (PubMed:22945023).
Sequence
MTRTPAAPEKHNRDSASRYKSGSKISTLFAEELVERSAIAGFGRKDLVVFDNACGTGAISSALHRALGDEKTRTWKLTCGDVSEAMVEVSKQKMIEEGWQNAEVEVVDAQNTGLLSDHYTHVFSAFGKMLGTQGNGIMLTSISAFNLFPDDKAAMEECFRVLQSGGTLAVSTWCSTVWATLIQSAIASIPGDLPTPTTEDIFGLYNKNWADESRVRAQFQQAGFTDINVTSVKKEYTVPVQELAEACKISLPHITRKFWTQEQRDSYEAEVPKAVLRILEEEQRGIGLGAMKAEAIIATARKP