title: A Novel Class of Plant Type III Polyketide Synthase Involved in Orsellinic Acid Biosynthesis fromRhododendron dauricum.
abstract: Rhododendron dauricumL. produces daurichromenic acid, the anti-HIV meroterpenoid consisting of sesquiterpene and orsellinic acid (OSA) moieties. To characterize the enzyme responsible for OSA biosynthesis, a cDNA encoding a novel polyketide synthase (PKS), orcinol synthase (ORS), was cloned from young leaves ofR. dauricum. The primary structure of ORS shared relatively low identities to those of PKSs from other plants, and the active site of ORS had a unique amino acid composition. The bacterially expressed, recombinant ORS accepted acetyl-CoA as the preferable starter substrate, and produced orcinol as the major reaction product, along with four minor products including OSA. The ORS identified in this study is the first plant PKS that generates acetate-derived aromatic tetraketides, such as orcinol and OSA. Interestingly, OSA production was clearly enhanced in the presence ofCannabis sativaolivetolic acid cyclase, suggesting that the ORS is involved in OSA biosynthesis together with an unidentified cyclase inR. dauricum.
authors.affiliation: Graduate School of Medicine and Pharmaceutical Sciences for Research, University of Toyama Toyama, Japan.
authors.forename: Futoshi
authors.initials: F
authors.lastname: Taura
authors.affiliation: Graduate School of Medicine and Pharmaceutical Sciences for Research, University of Toyama Toyama, Japan.
authors.forename: Miu
authors.initials: M
authors.lastname: Iijima
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyushu University Fukuoka, Japan.
authors.forename: Eriko
authors.initials: E
authors.lastname: Yamanaka
authors.affiliation: Institute of Pharmacognosy, Tokushima Bunri University Tokushima, Japan.
authors.forename: Hironobu
authors.initials: H
authors.lastname: Takahashi
authors.affiliation: Institute of Pharmacognosy, Tokushima Bunri University Tokushima, Japan.
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Kenmoku
authors.affiliation: Graduate School of Medicine and Pharmaceutical Sciences for Research, University of Toyama Toyama, Japan.
authors.forename: Haruna
authors.initials: H
authors.lastname: Saeki
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyushu University Fukuoka, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Morimoto
authors.affiliation: Institute of Pharmacognosy, Tokushima Bunri University Tokushima, Japan.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Asakawa
authors.affiliation: Graduate School of Medicine and Pharmaceutical Sciences for Research, University of Toyama Toyama, Japan.
authors.forename: Fumiya
authors.initials: F
authors.lastname: Kurosaki
authors.affiliation: Institute of Natural Medicine, University of Toyama Toyama, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Morita
keywords: Rhododendron dauricum; biosynthesis; daurichromenic acid; orcinol; orsellinic acid; plant type III polyketide synthase