The Enzyme Database

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EC 1.1.1.206     
Accepted name: tropinone reductase I
Reaction: tropine + NADP+ = tropinone + NADPH + H+
For diagram of reaction, click here
Glossary: tropine = 3α-hydroxytropane = tropan-3-endo-ol
Other name(s): tropine dehydrogenase; tropinone reductase (ambiguous); TR-I
Systematic name: tropine:NADP+ 3α-oxidoreductase
Comments: Also oxidizes other tropan-3α-ols, but not the corresponding β-derivatives [1]. This enzyme along with EC 1.1.1.236, tropinone reductase II, represents a branch point in tropane alkaloid metabolism [4]. Tropine (the product of EC 1.1.1.206) is incorporated into hyoscyamine and scopolamine whereas pseudotropine (the product of EC 1.1.1.236) is the first specific metabolite on the pathway to the calystegines [4]. Both enzymes are always found together in any given tropane-alkaloid-producing species, have a common substrate, tropinone, and are strictly stereospecific [3].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 118390-87-7
References:
1.  Koelen, K.J. and Gross, G.G. Partial purification and properties of tropine dehydrogenase from root cultures of Datura stramonium. Planta Med. 44 (1982) 227–230. [PMID: 17402126]
2.  Couladis, M.M, Friesen, J.B., Landgrebe, M.E. and Leete, E. Enzymes catalysing the reduction of tropinone to tropine and ψ-tropine isolated from the roots of Datura innoxia. Pytochemistry 30 (1991) 801–805.
3.  Nakajima, K., Hashimoto, T. and Yamada, Y. Two tropinone reductases with different stereospecificities are short-chain dehydrogenases evolved from a common ancestor. Proc. Natl. Acad. Sci. USA 90 (1993) 9591–9595. [DOI] [PMID: 8415746]
4.  Dräger, B. Tropinone reductases, enzymes at the branch point of tropane alkaloid metabolism. Phytochemistry 67 (2006) 327–337. [DOI] [PMID: 16426652]
[EC 1.1.1.206 created 1984, modified 2007]
 
 
EC 1.1.1.236     
Accepted name: tropinone reductase II
Reaction: pseudotropine + NADP+ = tropinone + NADPH + H+
For diagram of reaction, click here
Glossary: pseudotropine = ψ-tropine = 3β-hydroxytropane = tropan-3-exo-ol
Other name(s): tropinone (ψ-tropine-forming) reductase; pseudotropine forming tropinone reductase; tropinone reductase (ambiguous); TR-II
Systematic name: pseudotropine:NADP+ 3-oxidoreductase
Comments: This enzyme along with EC 1.1.1.206, tropine dehydrogenase, represents a branch point in tropane alkaloid metabolism [3]. Tropine (the product of EC 1.1.1.206) is incorporated into hyoscyamine and scopolamine whereas pseudotropine (the product of EC 1.1.1.236) is the first specific metabolite on the pathway to the calystegines [3]. Both enzymes are always found together in any given tropane-alkaloid-producing species, have a common substrate, tropinone, and are strictly stereospecific [2].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 136111-61-0
References:
1.  Dräger, B., Hashimoto, T. and Yamada, Y. Purification and characterization of pseudotropine forming tropinone reductase from Hyoscyamus niger root cultures. Agric. Biol. Chem. 52 (1988) 2663–2667.
2.  Couladis, M.M, Friesen, J.B., Landgrebe, M.E. and Leete, E. Enzymes catalysing the reduction of tropinone to tropine and ψ-tropine isolated from the roots of Datura innoxia. Pytochemistry 30 (1991) 801–805.
3.  Nakajima, K., Hashimoto, T. and Yamada, Y. Two tropinone reductases with different stereospecificities are short-chain dehydrogenases evolved from a common ancestor. Proc. Natl. Acad. Sci. USA 90 (1993) 9591–9595. [DOI] [PMID: 8415746]
4.  Dräger, B. Tropinone reductases, enzymes at the branch point of tropane alkaloid metabolism. Phytochemistry 67 (2006) 327–337. [DOI] [PMID: 16426652]
[EC 1.1.1.236 created 1992, modified 2007]
 
 
EC 1.1.1.293      
Deleted entry: tropinone reductase I. This enzyme was already in the Enzyme List as EC 1.1.1.206, tropine dehydrogenase so EC 1.1.1.293 has been withdrawn at the public-review stage
[EC 1.1.1.293 created 2007, withdrawn while undergoing public review]
 
 
EC 1.14.11.14      
Transferred entry: 6β-hydroxyhyoscyamine epoxidase. Now EC 1.14.20.13, 6β-hydroxyhyoscyamine epoxidase
[EC 1.14.11.14 created 1992, deleted 2018]
 
 
EC 1.14.20.13     
Accepted name: 6β-hydroxyhyoscyamine epoxidase
Reaction: (6S)-6β-hydroxyhyoscyamine + 2-oxoglutarate + O2 = scopolamine + succinate + CO2 + H2O
For diagram of tropane alkaloid biosynthesis, click here
Glossary: scopolamine = hyoscine = (1R,2R,4S,5S,7s)-9-methyl-3-oxa-9-azatricyclo[3.3.1.02,4]nonan-7-yl (2S)-3-hydroxy-2-phenylpropanoate
Other name(s): hydroxyhyoscyamine dioxygenase; (6S)-6-hydroxyhyoscyamine,2-oxoglutarate oxidoreductase (epoxide-forming)
Systematic name: (6S)-6β-hydroxyhyoscyamine,2-oxoglutarate:oxygen oxidoreductase (epoxide-forming)
Comments: Requires Fe2+ and ascorbate.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 121479-53-6
References:
1.  Hashimoto, T., Kohno, J. and Yamada, Y. 6β-Hydroxyhyoscyamine epoxidase from cultured roots of Hyoscyamus niger. Phytochemistry 28 (1989) 1077–1082.
[EC 1.14.20.13 created 1992 as EC 1.14.11.14, transferred 2018 to EC 1.14.20.13]
 
 


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