title: Justicidin B 7-hydroxylase, a cytochrome P450 monooxygenase from cell cultures of Linum perenne Himmelszelt involved in the biosynthesis of diphyllin.
abstract: Cell suspension cultures of Linum perenne L. Himmelszelt accumulate justicidin B as the main component together with glycosides of 7-hydroxyjusticidin B (diphyllin). A hypothetical biosynthetic pathway for these compounds is suggested. Justicidin B 7-hydroxylase (JusB7H) catalyzes the last step in the biosynthesis of diphyllin by introducing a hydroxyl group in position 7 of justicidin B. This enzyme was characterized from a microsomal fraction prepared from a Linum perenne Himmelszelt suspension culture for the first time. The hydroxylase activity was strongly inhibited by cytochrome c as well as other cytochrome P450 inhibitors like clotrimazole indicating the involvement of a cytochrome P450-dependent monooxygenase. JusB7H has a pH optimum of 7.4 and a temperature optimum of 26 degrees C. Justicidin B was the only substrate accepted by JusB7H with an apparent K(m) of 3.9+/-1.3 microM. NADPH is predominantly accepted as the electron donor, but NADH was a weak co-substrate. A synergistic effect of NADPH and NADH was not observed. The apparent K(m) for NADPH is 102+/-10 microM.
authors.affiliation: Institut für Entwicklungs- und Molekularbiologie der Pflanzen, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, D-40225 Düsseldorf, Germany.
authors.forename: Shiva
authors.initials: S
authors.lastname: Hemmati
authors.forename: Bernd
authors.initials: B
authors.lastname: Schneider
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Schmidt
authors.forename: Katja
authors.initials: K
authors.lastname: Federolf
authors.forename: A Wilhelm
authors.initials: AW
authors.lastname: Alfermann
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Fuss
mesh_terms: D052117:Benzodioxoles; D002478:Cells, Cultured; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004148:Dioxolanes / Q000737:chemistry / Q000378:metabolism*; D019597:Flax / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D006027:Glycosides / Q000378:metabolism; D007536:Isomerism; D017705:Lignans / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism*; D015394:Molecular Structure; D013379:Substrate Specificity
chemical_list: D052117:Benzodioxoles; D004148:Dioxolanes; D006027:Glycosides; D017705:Lignans; C049719:justicidins; D003577:Cytochrome P-450 Enzyme System; C010130:diphyllin