title: Molecular cloning and heterologous expression of a cDNA encoding berbamunine synthase, a C--O phenol-coupling cytochrome P450 from the higher plant Berberis stolonifera.
abstract: A cDNA encoding a cytochrome P450-dependent oxidase, berbamunine synthase (EC 1.1.3.34; CYP80), from cell suspension cultures of the higher plant Berberis stolonifera Koehne and Wolf (barberry) has been isolated and heterologously expressed in functional form in insect cell culture using a baculovirus-based expression system. This cytochrome P450-dependent enzyme is unusual in that it catalyzes the regio- and stereoselective formation of a C--O phenol couple in bisbenzylisoquinoline alkaloid biosynthesis without concomitant incorporation of activated oxygen into the product. Consistent with the function of an oxidase rather than a monooxygenase, an essential glycine residue in the distal helix, which forms the oxygen-binding pocket in the well-studied bacterial enzyme P-450cam, is replaced by proline at the equivalent position in berbamunine synthase. This oxidase was accumulated in an active form in insect cell microsomes and accepted electrons from the endogenous NADPH-cytochrome P450 reductase. The heterologously expressed enzyme oxidatively couples either two molecules of (R)-N-methylcoclaurine to form the (R,R) dimer guattegaumerine or one molecule each of (R)- and (S)-N-methylcoclaurine to form the (R,S) dimer berbamunine. The ratio of the two bisbenzylisoquinolines formed could be altered by reductase source or by varying the enantiomer composition of the substrates.
authors.affiliation: Laboratorium für Molekulare Biologie, Universität München, Germany.
authors.forename: P F
authors.initials: PF
authors.lastname: Kraus
authors.forename: T M
authors.initials: TM
authors.lastname: Kutchan
mesh_terms: D000429:Alcohol Oxidoreductases / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification; D000595:Amino Acid Sequence; D000818:Animals; D016367:Baculoviridae; D001483:Base Sequence; D002478:Cells, Cultured; D003001:Cloning, Molecular / Q000379:methods; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000737:chemistry / Q000302:isolation & purification; D017931:DNA Primers; D018076:DNA, Complementary; D007700:Kinetics; D008861:Microsomes / Q000201:enzymology*; D008969:Molecular Sequence Data; D010944:Plants / Q000201:enzymology* / Q000235:genetics; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid; D013053:Spectrophotometry; D018411:Spodoptera; D013698:Templates, Genetic; D014162:Transfection
chemical_list: D017931:DNA Primers; D018076:DNA, Complementary; D011994:Recombinant Proteins; C092555:cytochrome P-450 CYP80A1 (Berberis stolonifera); D003577:Cytochrome P-450 Enzyme System; D000429:Alcohol Oxidoreductases