Isoquinoline alkaloids are tyrosine-derived plant alkaloids with an isoquinoline skeleton. Among them benzylisoquinoline alkaloids form an important group with potent pharmacological activity, including analgesic compounds of morphine and codeine, and anti-infective agents of berberine, palmatine, and magnoflorine. Biosynthesis of isoquinoline alkaloids proceeds via decarboxylation of tyrosine or DOPA to yield dopamine, which together with 4-hydroxyphenylacetaldehyde, an aldehyde derived from tyrosine, is converted to reticuline, an important precursor of various benzylisoquinoline alkaloids.

Metabolism; Biosynthesis of other secondary metabolites
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PMID:10811648

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Molecular characterization of the S-adenosyl-L-methionine:3'-hydroxy-N-methylcoclaurine 4'-O-methyltransferase involved in isoquinoline alkaloid biosynthesis in Coptis japonica.

J Biol Chem 275:23398-405 (2000)
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PMID:12423366

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Molecular cloning of columbamine O-methyltransferase from cultured Coptis japonica cells.

Eur J Biochem 269:5659-67 (2002)
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(R,S)-Reticuline 7-O-methyltransferase and (R,S)-norcoclaurine 6-O-methyltransferase of Papaver somniferum - cDNA cloning and characterization of methyl transfer enzymes of alkaloid biosynthesis in opium poppy.

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Molecular cloning and characterization of CYP80G2, a cytochrome P450 that catalyzes an intramolecular C-C phenol coupling of (S)-reticuline in magnoflorine biosynthesis, from cultured Coptis japonica cells.

J Biol Chem 283:8810-21 (2008)
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Proc Natl Acad Sci U S A 105:7393-8 (2008)
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The formation of corydaline and related alkaloids in Corydalis cava in vivo and in vitro.

Can J Chem 72:170-175 (1994)
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Sekine Y, Crevelling C, Bell M, Brossi A.

Mammalian alkaloids: O-methylation of (+-)-norcoclaurine-1-carboxylic acid and related isoquinolines including (S)- and (R)-norcoclaurine with 14C-labeled S-adenosyl-L-methionine in presence of mammalian catechol O-methyltransferase.

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Enzymic 10-hydroxylation and 10-O-methylation of dihydrosanguinarine in dihydrochelirubine formation by Eschscholtzia.

Phytochemistry 31:2713-2717 (1992)
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Enzymic 12-hydroxylation and 12-O-methylation of dihydrochelirubine in dihydromacarpine formation by Thalictrum bulgaricum.

Phytochemistry 36:1409-1416 (1994)
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PMID:24241413

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Partial purification and characterization of dihydrobenzophenanthridine oxidase from Eschscholtzia californica cell suspension cultures.

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