title: Production of a novel O-methyl-isoflavone by regioselective sequential hydroxylation and O-methylation reactions in Streptomyces avermitilis host system.
abstract: Distinct isoflavone O-methyltransferases (IOMTs) from Streptomyces species were isolated and expressed using S. avermitilis host system. Previously reported isoflavone 7-O-methyltransferases (I7OMTs, E.C. 2.1.1.150) and two putative O-methyltransferases (OMTs) from Saccharopolyspora erythraea were selected by comparative sequence grouping and expressed in S. avermitilisΔSaOMT2 under the control of constitutive ermE promoter. During whole-cell biotransformation of 4',7-dihydroxyisoflavone (daidzein) by constructed recombinant strains, production of O-methylated daidzein was investigated. S. avermitilisΔSaOMT2::SeOMT3 (SeOMT3) produced 7-methoxy-4'-hydroxyisoflavone (7-OMD) with 4.5% of low conversion yield due to competitive oxidation reactions. However, SeOMT3 could produce a novel 4',7-dihydroxy-3'-methoxyisoflavone (3'-OMD) (<1%) resulted from subsequent 3'-O-methylation of 3',4',7-trihydroxyisoflavone (3'-OHD) which was a hydroxylated product catalyzed by oxygenases. Although external addition of SAM did not change the conversion yield of O-methylation reaction, co-expression of SAM synthetase gene (metK) with SeOMT3 greatly induced the regiospecific O-methylation reaction at 3'-hydroxyl group with final conversion of 12.1% using 0.1 mM of daidzein.
authors.affiliation: School of Chemical and Biological Engineering, Institute of Bioengineering, Seoul National University, Seoul, South Korea.
authors.forename: Kwon-Young
authors.initials: KY
authors.lastname: Choi
authors.forename: EunOk
authors.initials: E
authors.lastname: Jung
authors.forename: Yung-Hun
authors.initials: YH
authors.lastname: Yang
authors.forename: Byung-Gee
authors.initials: BG
authors.lastname: Kim
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001709:Biotechnology; D008401:Gas Chromatography-Mass Spectrometry; D006900:Hydroxylation; D007529:Isoflavones / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D008716:Methionine Adenosyltransferase / Q000235:genetics / Q000378:metabolism; D008745:Methylation; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D012436:S-Adenosylmethionine / Q000378:metabolism; D016415:Sequence Alignment; D013237:Stereoisomerism; D013302:Streptomyces / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D007529:Isoflavones; C004742:daidzein; D012436:S-Adenosylmethionine; D008780:Methyltransferases; D008716:Methionine Adenosyltransferase
keywords: O-methyltransferase; SAM; Streptomyces; daidzein; metK; oxygenase