title: Enantioselective microbial synthesis of the indigenous natural product (-)-α-bisabolol by a sesquiterpene synthase from chamomile (Matricaria recutita).
abstract: (-)-α-Bisabolol, a sesquiterpene alcohol, is a major ingredient in the essential oil of chamomile (Matricaria recutita) and is used in many health products. The current supply of (-)-α-bisabolol is mainly dependent on the Brazilian candeia tree (Eremanthus erythropappus) by distillation or by chemical synthesis. However, the distillation method using the candeia tree is not sustainable, and chemical synthesis suffers from impurities arising from undesirable α-bisabolol isomers. Therefore enzymatic synthesis of (-)-α-bisabolol is a viable alternative. In the present study, a cDNA encoding (-)-α-bisabolol synthase (MrBBS) was identified from chamomile and used for enantioselective (-)-α-bisabolol synthesis in yeast. Chamomile MrBBS was identified by Illumina and 454 sequencing, followed by activity screening in yeast. When MrBBS was expressed in yeast, 8 mg of α-bisabolol was synthesized de novo per litre of culture. The structure of purified α-bisabolol was elucidated as (S,S)-α-bisabolol [or (-)-α-bisabolol]. Although MrBBS possesses a putative chloroplast-targeting peptide, it was localized in the cytosol, and a deletion of its N-terminal 23 amino acids significantly reduced its stability and activity. Recombinant MrBBS showed kinetic properties comparable with those of other sesquiterpene synthases. These data provide compelling evidence that chamomile MrBBS synthesizes enantiopure (-)-α-bisabolol as a single sesquiterpene product, opening a biotechnological opportunity to produce (-)-α-bisabolol.
authors.affiliation: *Department of Agricultural Biotechnology and Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul 151-921, South Korea.
authors.forename: Young-Jin
authors.initials: YJ
authors.lastname: Son
authors.affiliation: †Department of Biological Sciences, University of Calgary, Calgary, Canada, T2N 1N4.
authors.forename: Moonhyuk
authors.initials: M
authors.lastname: Kwon
authors.affiliation: †Department of Biological Sciences, University of Calgary, Calgary, Canada, T2N 1N4.
authors.forename: Dae-Kyun
authors.initials: DK
authors.lastname: Ro
authors.forename: Soo-Un
authors.initials: SU
authors.lastname: Kim
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D007700:Kinetics; D031168:Matricaria / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D000081222:Monocyclic Sesquiterpenes; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012717:Sesquiterpenes / Q000737:chemistry / Q000378:metabolism*; D013237:Stereoisomerism; D013379:Substrate Specificity; D015003:Yeasts / Q000235:genetics / Q000378:metabolism*
chemical_list: D000081222:Monocyclic Sesquiterpenes; D010940:Plant Proteins; D012717:Sesquiterpenes; C004497:bisabolol; D019883:Alkyl and Aryl Transferases; C108877:terpene synthase