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, tropinone reductase I, 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. [PMID: 8415746]
4. Dräger, B. Tropinone reductases, enzymes at the branch point of tropane alkaloid metabolism. Phytochemistry 67 (2006) 327-337. [PMID: 16426652]