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 2.3.1.185     
Accepted name: tropine acyltransferase
Reaction: an acyl-CoA + tropine = CoA + an O-acyltropine
For diagram of tropane alkaloid biosynthesis, click here
Glossary: tropine = tropan-3α-ol = 3α-hydroxytropane
Other name(s): tropine:acyl-CoA transferase; acetyl-CoA:tropan-3-ol acyltransferase; tropine acetyltransferase; tropine tigloyltransferase; TAT
Systematic name: acyl-CoA:tropine O-acyltransferase
Comments: This enzyme exhibits absolute specificity for the endo/3α configuration found in tropine as pseudotropine (tropan-3β-ol; see EC 2.3.1.186, pseudotropine acyltransferase) is not a substrate [3]. Acts on a wide range of aliphatic acyl-CoA derivatives, with tigloyl-CoA and acetyl-CoA being the best substrates. It is probably involved in the formation of the tropane alkaloid littorine, which is a precursor of hyoscyamine [4].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 138440-79-6, 162535-29-7
References:
1.  Robins, R.J., Bachmann, P., Robinson, T., Rhodes, M.J. and Yamada, Y. The formation of 3α- and 3β-acetoxytropanes by Datura stramonium transformed root cultures involves two acetyl-CoA-dependent acyltransferases. FEBS Lett. 292 (1991) 293–297. [DOI] [PMID: 1959620]
2.  Robins, R.J., Bachmann,P., Peerless, A.C.J. and Rabot, S. Esterification reactions in the biosynthesis of tropane alkaloids in transformed root cultures. Plant Cell, Tissue Organ Cult. 38 (1994) 241–247.
3.  Boswell, H.D., Dräger, B., McLauchlan, W.R., Portsteffen, A., Robins, D.J., Robins, R.J. and Walton, N.J. Specificities of the enzymes of N-alkyltropane biosynthesis in Brugmansia and Datura. Phytochemistry 52 (1999) 871–878. [DOI] [PMID: 10626376]
4.  Li, R., Reed, D.W., Liu, E., Nowak, J., Pelcher, L.E., Page, J.E. and Covello, P.S. Functional genomic analysis of alkaloid biosynthesis in Hyoscyamus niger reveals a cytochrome P450 involved in littorine rearrangement. Chem. Biol. 13 (2006) 513–520. [DOI] [PMID: 16720272]
[EC 2.3.1.185 created 2008]
 
 
EC 2.3.1.186     
Accepted name: pseudotropine acyltransferase
Reaction: an acyl-CoA + pseudotropine = CoA + an O-acylpseudotropine
For diagram of tropane alkaloid biosynthesis, click here
Glossary: tropine = tropan-3β-ol = 3β-hydroxytropane
Other name(s): pseudotropine:acyl-CoA transferase; tigloyl-CoA:pseudotropine acyltransferase; acetyl-CoA:pseudotropine acyltransferase; pseudotropine acetyltransferase; pseudotropine tigloyltransferase; PAT (ambiguous)
Systematic name: acyl-CoA:pseudotropine O-acyltransferase
Comments: This enzyme exhibits absolute specificity for the exo/3β configuration found in pseudotropine as tropine (tropan-3α-ol; see EC 2.3.1.185, tropine acyltransferase) and nortropine are not substrates [1]. Acts on a wide range of aliphatic acyl-CoA derivatives, including acetyl-CoA, β-methylcrotonyl-CoA and tigloyl-CoA [1].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 138440-78-5, 162535-26-4
References:
1.  Rabot, S., Peerless, A.C.J. and Robins, R.J. Tigloyl-CoA:pseudotropine acyltransferase — an enzyme of tropane alkaloid biosynthesis. Phytochemistry 39 (1995) 315–322.
2.  Robins, R.J., Bachmann, P., Robinson, T., Rhodes, M.J. and Yamada, Y. The formation of 3α- and 3β-acetoxytropanes by Datura stramonium transformed root cultures involves two acetyl-CoA-dependent acyltransferases. FEBS Lett. 292 (1991) 293–297. [DOI] [PMID: 1959620]
3.  Robins, R.J., Bachmann,P., Peerless, A.C.J. and Rabot, S. Esterification reactions in the biosynthesis of tropane alkaloids in transformed root cultures. Plant Cell, Tissue Organ Cult. 38 (1994) 241–247.
4.  Boswell, H.D., Dräger, B., McLauchlan, W.R., Portsteffen, A., Robins, D.J., Robins, R.J. and Walton, N.J. Specificities of the enzymes of N-alkyltropane biosynthesis in Brugmansia and Datura. Phytochemistry 52 (1999) 871–878. [DOI] [PMID: 10626376]
[EC 2.3.1.186 created 2008]
 
 


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