The Enzyme Database

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EC 1.5.1.27     
Accepted name: 1,2-dehydroreticulinium reductase (NADPH)
Reaction: (R)-reticuline + NADP+ = 1,2-dehydroreticulinium + NADPH + H+
For diagram of thebaine biosynthesis, click here
Other name(s): 1,2-dehydroreticulinium ion reductase
Systematic name: (R)-reticuline:NADP+ oxidoreductase
Comments: Reduces the 1,2-dehydroreticulinium ion to (R)-reticuline, which is a direct precursor of morphinan alkaloids in the poppy plant. The enzyme does not catalyse the reverse reaction to any significant extent under physiological conditions.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 130590-58-8
References:
1.  De-Eknamkul, W. and Zenk, M.H. Purification and properties of 1,2-dehydroreticulinium reductase from Papaver somniferum seedlings. Phytochemistry 31 (1992) 813–821.
[EC 1.5.1.27 created 1999, modified 2004]
 
 
EC 1.14.19.54     
Accepted name: 1,2-dehydroreticuline synthase
Reaction: (S)-reticuline + [reduced NADPH—hemoprotein reductase] + O2 = 1,2-dehydroreticuline + [oxidized NADPH—hemoprotein reductase] + 2 H2O
For diagram of thebaine biosynthesis, click here
Glossary: reticuline = 1-(3-hydroxy-4-methoxybenzyl)-6-methoxy-2-methyl-1,2,3,4-tetrahydroisoquinolin-7-ol
Other name(s): STORR; CYP82Y2 (gene name); DRS (gene name)
Systematic name: (S)-reticuline,[reduced NADPH—hemoprotein reductase]:oxygen 1,2-oxidoreductase
Comments: A P-450 (heme-thiolate) cytochrome. The enzyme from Papaver rhoeas (field poppy) is specific for (S)-reticuline and does not act on the (R)-form. The enzyme from Papaver somniferum (opium poppy), which is involved in the biosynthesis of morphine and related alkaloids, forms a fusion protein with EC 1.5.1.27, 1,2-dehydroreticulinium reductase (NADPH), which catalyses the reduction of 1,2-dehydroreticuline to (R)-reticuline, thus forming an epimerase system that converts (S)-reticuline to (R)-reticuline.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Hirata, K., Poeaknapo, C., Schmidt, J. and Zenk, M.H. 1,2-Dehydroreticuline synthase, the branch point enzyme opening the morphinan biosynthetic pathway. Phytochemistry 65 (2004) 1039–1046. [DOI] [PMID: 15110683]
2.  Winzer, T., Kern, M., King, A.J., Larson, T.R., Teodor, R.I., Donninger, S.L., Li, Y., Dowle, A.A., Cartwright, J., Bates, R., Ashford, D., Thomas, J., Walker, C., Bowser, T.A. and Graham, I.A. Morphinan biosynthesis in opium poppy requires a P450-oxidoreductase fusion protein. Science 349 (2015) 309–312. [DOI] [PMID: 26113639]
3.  Farrow, S.C., Hagel, J.M., Beaudoin, G.A., Burns, D.C. and Facchini, P.J. Stereochemical inversion of (S)-reticuline by a cytochrome P450 fusion in opium poppy. Nat. Chem. Biol. 11 (2015) 728–732. [DOI] [PMID: 26147354]
[EC 1.14.19.54 created 2018]
 
 
EC 1.14.19.67     
Accepted name: salutaridine synthase
Reaction: (R)-reticuline + [reduced NADPH—hemoprotein reductase] + O2 = salutaridine + [oxidized NADPH—hemoprotein reductase] + 2 H2O
For diagram of thebaine biosynthesis, click here
Other name(s): (R)-reticuline oxidase (C-C phenol-coupling)
Systematic name: (R)-reticuline,[reduced NADPH—hemoprotein reductase]:oxygen oxidoreductase (C-C phenol-coupling)
Comments: A cytochrome P-450 (heme-thiolate) protein found in plants. Forms the morphinan alkaloid salutaridine by intramolecular phenol oxidation of reticuline without the incorporation of oxygen into the product.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 149433-84-1
References:
1.  Gerady, R. and Zenk, M.H. Formation of salutaridine from (R)-reticuline by a membrane-bound cytochrome P-450 enzyme from Papaver somniferum. Phytochemistry 32 (1993) 79–86.
[EC 1.14.19.67 created 1999 as EC 1.1.3.35, transferred 2002 to EC 1.14.21.4, transferred 2018 to EC 1.14.19.67]
 
 
EC 1.14.21.4      
Transferred entry: salutaridine synthase. Now EC 1.14.19.67, salutaridine synthase
[EC 1.14.21.4 created 2002, deleted 2018]
 
 
EC 2.1.1.291     
Accepted name: (R,S)-reticuline 7-O-methyltransferase
Reaction: (1) S-adenosyl-L-methionine + (S)-reticuline = S-adenosyl-L-homocysteine + (S)-laudanine
(2) S-adenosyl-L-methionine + (R)-reticuline = S-adenosyl-L-homocysteine + (R)-laudanine
For diagram of laudanine biosynthesis, click here
Glossary: (S)-reticuline = (1S)-1-[(3-hydroxy-4-methoxyphenyl)methyl]-6-methoxy-2-methyl-1,2,3,4-tetrahydroisoquinolin-7-ol
(R)-reticuline = (1R)-1-[(3-hydroxy-4-methoxyphenyl)methyl]-6-methoxy-2-methyl-1,2,3,4-tetrahydroisoquinolin-7-ol
(S)-laudanine = 5-[((1S)-6,7-dimethoxy-2-methyl-1,2,3,4-tetrahydroisoquinolin-1-yl)methyl]-2-methoxyphenol
(R)-laudanine = 5-[((1R)-6,7-dimethoxy-2-methyl-1,2,3,4-tetrahydroisoquinolin-1-yl)methyl]-2-methoxyphenol
Systematic name: S-adenosyl-L-methionine:(R,S)-reticuline 7-O-methyltransferase
Comments: The enzyme from the plant Papaver somniferum (opium poppy) methylates (S)- and (R)-reticuline with equal efficiency and is involved in the biosynthesis of tetrahydrobenzylisoquinoline alkaloids.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Ounaroon, A., Decker, G., Schmidt, J., Lottspeich, F. and Kutchan, T.M. (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. Plant J. 36 (2003) 808–819. [DOI] [PMID: 14675446]
2.  Weid, M., Ziegler, J. and Kutchan, T.M. The roles of latex and the vascular bundle in morphine biosynthesis in the opium poppy, Papaver somniferum. Proc. Natl. Acad. Sci. USA 101 (2004) 13957–13962. [DOI] [PMID: 15353584]
[EC 2.1.1.291 created 2013]
 
 
EC 2.1.1.337     
Accepted name: reticuline N-methyltransferase
Reaction: (1) S-adenosyl-L-methionine + (S)-reticuline = S-adenosyl-L-homocysteine + (S)-tembetarine
(2) S-adenosyl-L-methionine + (S)-corytuberine = S-adenosyl-L-homocysteine + (S)-magnoflorine
For diagram of corytuberine and magnoflorine biosynthesis, click here and for diagram of tembetarine biosynthesis, click here
Glossary: (S)-reticuline = (1S)-1-(3-hydroxy-4-methoxybenzyl)-6-methoxy-2-methyl-1,2,3,4-tetrahydroisoquinolin-7-ol
(S)-tembetarine = (1S)-1-(3-hydroxy-4-methoxybenzyl)-6-methoxy-2,2-dimethyl-1,2,3,4-tetrahydroisoquinolin-7-ol
(S)-corytuberine = (6aS)-2,10-dimethoxy-6-methyl-5,6,6a,7-tetrahydro-4H-dibenzo[de,g]quinoline-1,11-diol
(S)-magnoflorine = (6aS)-1,11-dihydroxy-2,10-dimethoxy-6,6-dimethyl-5,6,6a,7-tetrahydro-4H-dibenzo[de,g]quinolinium
Other name(s): RNMT
Systematic name: S-adenosyl-L-methionine:(S)-reticuline N-methyltransferase
Comments: The enzyme from opium poppy (Papaver somniferum) can also methylate (R)-reticuline, tetrahydropapaverine, (S)-glaucine and (S)-bulbocapnine. It is involved in the biosynthesis of the quaternary benzylisoquinoline alkaloid magnoflorine.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Morris, J.S. and Facchini, P.J. Isolation and characterization of reticuline N-methyltransferase involved in biosynthesis of the aporphine alkaloid magnoflorine in opium poppy. J. Biol. Chem. 291 (2016) 23416–23427. [DOI] [PMID: 27634038]
[EC 2.1.1.337 created 2017]
 
 


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