title: A plant type III polyketide synthase that produces pentaketide chromone.
abstract: A novel plant-specific type III polyketide synthase (PKS) that catalyzes formation of a pentaketide chromone, 5,7-dihydroxy-2-methylchromone, from five molecules of malonyl-CoA, was cloned and sequenced from aloe (Aloe arborescens). Site-directed mutagenesis revealed that Met207 (corresponding to Thr197 in CHS) determines the polyketide chain length and the product specificity of the enzyme; remarkably, replacement of a single amino acid residue, Met207, with Gly yielded a mutant enzyme that efficiently produces aromatic octaketides, SEK4 and SEK4b, the products of the minimal PKS for actinorhodin (act from Streptomyces coelicolor), from eight molecules of malonyl-CoA. This provided new insights into the catalytic functions and specificities of the CHS-superfamily type III PKS enzymes.
authors.affiliation: School of Pharmaceutical Sciences and the COE 21 Program, University of Shizuoka, Shizuoka 422-8526, Japan. abei@ys7.u-shizuoka-ken.ac.jp
authors.forename: Ikuro
authors.initials: I
authors.lastname: Abe
authors.forename: Yoriko
authors.initials: Y
authors.lastname: Utsumi
authors.forename: Satoshi
authors.initials: S
authors.lastname: Oguro
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Morita
authors.forename: Yukie
authors.initials: Y
authors.lastname: Sano
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Noguchi
mesh_terms: D000217:Acyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000504:Aloe / Q000201:enzymology / Q000235:genetics; D000595:Amino Acid Sequence; D002867:Chromones / Q000378:metabolism*; D007700:Kinetics; D008316:Malonyl Coenzyme A / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D002867:Chromones; D010940:Plant Proteins; D008316:Malonyl Coenzyme A; D000217:Acyltransferases; C020141:flavanone synthetase