title: Dirigent-mediated podophyllotoxin biosynthesis in Linum flavum and Podophyllum peltatum.
abstract: Given the importance of the antitumor/antiviral lignans, podophyllotoxin and 5-methoxypodophyllotoxin, as biotechnological targets, their biosynthetic pathways were investigated in Podophyllum peltatum and Linum flavum. Entry into their pathways was established to occur via dirigent mediated coupling of E-coniferyl alcohol to afford (+)-pinoresinol; the encoding gene was cloned and the recombinant protein subsequently obtained. Radiolabeled substrate studies using partially purified enzyme preparations next revealed (+)-pinoresinol was enantiospecifically converted sequentially into (+)-lariciresinol and (-)-secoisolariciresinol via the action of an NADPH-dependent bifunctional pinoresinol/lariciresinol reductase. The resulting (-)-secoisolariciresinol was enantiospecifically dehydrogenated into (-)-matairesinol, as evidenced through the conversion of both radio- and stable isotopically labeled secoisolariciresinol into matairesinol, this being catalyzed by the NAD-dependent secoisolariciresinol dehydrogenase. (-)-Matairesinol was further hydroxylated to afford 7'-hydroxymatairesinol, this being efficiently metabolized into 5-methoxypodophyllotoxin. Thus much of the overall biosynthetic pathway to podophyllotoxin has been established, that is, from the dirigent mediated coupling of E-coniferyl alcohol to the subsequent conversions leading to 7'-hydroxymatairesinol.
authors.affiliation: Institute of Biological Chemistry, Washington State University, Pullman 99164-6340, USA.
authors.forename: Z Q
authors.initials: ZQ
authors.lastname: Xia
authors.forename: M A
authors.initials: MA
authors.lastname: Costa
authors.forename: J
authors.initials: J
authors.lastname: Proctor
authors.forename: L B
authors.initials: LB
authors.lastname: Davin
authors.forename: N G
authors.initials: NG
authors.lastname: Lewis
mesh_terms: D000595:Amino Acid Sequence; D000970:Antineoplastic Agents / Q000378:metabolism; D001483:Base Sequence; D018744:DNA, Plant / Q000032:analysis; D019597:Flax / Q000235:genetics / Q000378:metabolism*; D005663:Furans / Q000378:metabolism; D017705:Lignans / Q000378:metabolism; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D010946:Plants, Medicinal; D010947:Plants, Toxic; D011034:Podophyllotoxin / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D011035:Podophyllum / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D000970:Antineoplastic Agents; D018744:DNA, Plant; D005663:Furans; D017705:Lignans; D010940:Plant Proteins; C068935:matairesinol; D011034:Podophyllotoxin