title: The first plant type III polyketide synthase that catalyzes formation of aromatic heptaketide.
abstract: A cDNA encoding a novel plant type III polyketide synthase (PKS) was cloned from rhubarb (Rheum palmatum). A recombinant enzyme expressed in Escherichia coli accepted acetyl-CoA as a starter, carried out six successive condensations with malonyl-CoA and subsequent cyclization to yield an aromatic heptaketide, aloesone. The enzyme shares 60% amino acid sequence identity with chalcone synthases (CHSs), and maintains almost identical CoA binding site and catalytic residues conserved in the CHS superfamily enzymes. Further, homology modeling predicted that the 43-kDa protein has the same overall fold as CHS. This provides new insights into the catalytic functions of type III PKSs, and suggests further involvement in the biosynthesis of plant polyketides.
authors.affiliation: School of Pharmaceutical Sciences, and the 21st Century COE Program, University of Shizuoka, 52-1 Yada, Shizuoka 422-8526, Japan. abei@ys7.u-shizouka-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: Hiroshi
authors.initials: H
authors.lastname: Noguchi
mesh_terms: D000105:Acetyl Coenzyme A / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D002384:Catalysis; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D008316:Malonyl Coenzyme A / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009097:Multienzyme Complexes / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D012250:Rheum / Q000737:chemistry / Q000201:enzymology*; D016415:Sequence Alignment
chemical_list: D009097:Multienzyme Complexes; D010940:Plant Proteins; D008316:Malonyl Coenzyme A; D000105:Acetyl Coenzyme A