title: Identification of csypyrone B2 and B3 as the minor products of Aspergillus oryzae type III polyketide synthase CsyB.
abstract: Since our first report on the identification of the fungal type III polyketide synthase (PKS) genes csyA~D in Aspergillus oryzae RIB40, type III PKS homologues have also been found in other fungal species. We previously reported the isolation and structural determination of csypyrone B1 as the main product of CsyB when inductively expressed in Aspergillus oryzae. Herein we report the isolation and identification of the two minor products of the csyB transformant in addition to csypyrone B1 as 4-(3-acetyl-4-hydroxy-2-oxo-2H-pyran-6-yl)butyric acid and 5-(3-acetyl-4-hydroxy-2-oxo-2H-pyran-6-yl)pentanoic acid. These compounds were named csypyrone B2 and B3, respectively, and both are homologues of main product csypyrone B1 with different side chain lengths. This result suggests that the carbon skeleton of the csypyrone B precursor is constructed by the condensation of fatty acyl-CoA and acetylmalonyl-CoA followed by pyrone formation. The alkyl side chain of the precursor may be oxidatively cleaved by enzyme(s) in the host fungus to give variations of csypyrone B with propanoic acid, butyric acid, or pentanoic acid side chains.
authors.affiliation: School of Pharmacy, Iwate Medical University, 2-1-1 Nishitokuta, Yahaba, Iwate 028-3694, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Hashimoto
authors.forename: Yasuyo
authors.initials: Y
authors.lastname: Seshime
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Kitamoto
authors.forename: Nahoko
authors.initials: N
authors.lastname: Uchiyama
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Goda
authors.forename: Isao
authors.initials: I
authors.lastname: Fujii
mesh_terms: D001236:Aspergillus oryzae / Q000737:chemistry*; D002087:Butyrates / Q000737:chemistry* / Q000302:isolation & purification; D015394:Molecular Structure; D010421:Pentanoic Acids / Q000737:chemistry* / Q000302:isolation & purification; D048630:Polyketide Synthases / Q000737:chemistry*; D011422:Propionates / Q000737:chemistry*; D011753:Pyrones / Q000737:chemistry* / Q000302:isolation & purification
chemical_list: D002087:Butyrates; D010421:Pentanoic Acids; D011422:Propionates; D011753:Pyrones; C552777:csypyrone B1; D048630:Polyketide Synthases