title: Identification of csypyrone B1 as the novel product of Aspergillus oryzae type III polyketide synthase CsyB.
abstract: As a novel superfamily of type III polyketide synthases (PKSs) in microbes, four genes, csyA, csyB, csyC, and csyD, were found in the genome of Aspergillus oryzae, an industrially important filamentous fungus. Although orthologs of csyA, csyC, and csyD genes are present in a closely related species, Aspergillus flavus, csyB gene is unique to A. oryzae. To identify its function, we carried out overexpression of csyB gene under the control of alpha-amylase promoter in A. oryzae. 3-(3-Acetyl-4-hydroxy-2-oxo-2H-pyran-6-yl)propanoic acid, named csypyrone B1, was identified as a CsyB product. Feeding experiments of (13)C-labeled acetate indicated that five acetate units were incorporated into csypyrone B1. Two possible mechanisms are proposed for the biosynthesis of cycpyrone B1: (1) condensation of succinyl-CoA with three acetyl/malonyl-CoAs, and the following pyrone ring cyclization; (2) condensation of butyryl-CoA with three acetyl/malonyl-CoAs, and the following pyrone ring cyclization and side-chain oxidation.
authors.affiliation: School of Pharmacy, Iwate Medical University, Yahaba, Iwate 028-3694, Japan.
authors.forename: Yasuyo
authors.initials: Y
authors.lastname: Seshime
authors.forename: Praveen Rao
authors.initials: PR
authors.lastname: Juvvadi
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Kitamoto
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Ebizuka
authors.forename: Isao
authors.initials: I
authors.lastname: Fujii
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism; D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism*; D001231:Aspergillus flavus / Q000201:enzymology; D001236:Aspergillus oryzae / Q000201:enzymology*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D016681:Genome, Fungal; D011422:Propionates / Q000737:chemistry / Q000378:metabolism*; D011753:Pyrones / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000214:Acyl Coenzyme A; D005656:Fungal Proteins; D011422:Propionates; D011753:Pyrones; D011994:Recombinant Proteins; C552777:csypyrone B1; C024343:butyryl-coenzyme A; C012046:succinyl-coenzyme A; D000217:Acyltransferases; C020141:flavanone synthetase