title: CYP82Y1 is N-methylcanadine 1-hydroxylase, a key noscapine biosynthetic enzyme in opium poppy.
abstract: Noscapine is a phthalideisoquinoline alkaloid investigated for its potent pharmacological properties. Although structurally elucidated more than a century ago, the biosynthesis of noscapine has not been established. Radiotracer studies have shown that noscapine is derived from the protoberberine alkaloid (S)-scoulerine and has been proposed to proceed through (S)-N-methylcanadine. However, pathway intermediates involved in the conversion of N-methylcanadine to noscapine have not been identified. We report the isolation and characterization of the cytochrome P-450 CYP82Y1, which catalyzes the 1-hydroxylation of N-methylcanadine to 1-hydroxy-N-methylcanadine. Comparison of transcript and metabolite profiles of eight opium poppy chemotypes revealed four cytochrome P-450s, three from the CYP82 and one from the CYP719 families, that were tightly correlated with noscapine accumulation. Recombinant CYP82Y1 was the only enzyme that accepted (R,S)-N-methylcanadine as a substrate with strict specificity and high affinity. As expected, CYP82Y1 was abundantly expressed in opium poppy stems where noscapine accumulation is highest among plant organs. Suppression of CYP82Y1 using virus-induced gene silencing caused a significant reduction in the levels of noscapine, narcotoline, and a putative downstream secoberbine intermediate and also resulted in increased accumulation of the upstream pathway intermediates scoulerine, tetrahydrocolum-bamine, canadine, and N-methylcanadine. The combined biochemical and physiological data support the 1-hydroxylation of (S)-N-methylcanadine catalyzed by CYP82Y1 as the first committed step in the formation of noscapine in opium poppy.
authors: From the University of Calgary Department of Biological Sciences, Calgary, Alberta T2N 1N4, Canada.
authors: Thu-Thuy T
authors: TT
authors: Dang
authors: Peter J
authors: PJ
authors: Facchini
mesh_terms: D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D009665:Noscapine / Q000378:metabolism*; D010207:Papaver / Q000201:enzymology* / Q000235:genetics; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D011994:Recombinant Proteins; D009665:Noscapine; D003577:Cytochrome P-450 Enzyme System
keywords: Biosynthesis; Cytochrome P-450; Enzyme Catalysis; Gene Silencing; Metabolism; Plant Biochemistry; Secondary Metabolism