noscapine and tetrahydrocolumbamine

Noscapine biosynthesis in opium poppy is thought to occur via N-methylcanadine, which would be produced through 9-O-methylation of (S)-scoulerine, methylenedioxy bridge formation on (S)-tetrahydrocolumbamine, and N-methylation of (S)-canadine. Only scoulerine 9-O-methyltransferase has been functionally characterized. We report the isolation and characterization of a cytochrome P450 (CYP719A21) from opium poppy that converts (S)-tetrahydrocolumbamine to (S)-canadine. Recombinant CYP719A21 displayed strict substrate specificity and high affinity (Km=4.63±0.71 μM) for (S)-tetrahydrocolumbamine. Virus-induced gene silencing of CYP719A21 caused a significant increase in (S)-tetrahydrocolumbamine accumulation and a corresponding decrease in the levels of putative downstream intermediates and noscapine in opium poppy plants.

Topics: Amino Acid Sequence; Berberine; Berberine Alkaloids; Biosynthetic Pathways; Chromatography, Liquid; Cloning, Molecular; Cytochrome P-450 Enzyme System; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Gene Silencing; Immunoblotting; Mass Spectrometry; Molecular Sequence Data; Molecular Structure; Noscapine; Papaver; Phylogeny; Plant Proteins; Reverse Transcriptase Polymerase Chain Reaction; Sequence Homology, Amino Acid; Substrate Specificity