Tropinone reductase (TR)

Tropinone reductases (TRs) are specialized enzymes within the short-chain dehydrogenase/reductase (SDR) superfamily that play a critical role in the biosynthesis of tropane alkaloids (Nakajima et al., 1993). These enzymes are primarily found in the Solanaceae plant family and are responsible for the stereospecific reduction of tropinone using NADPH as a cofactor (Yamada et al., 2003). There are two main isoforms: Tropinone Reductase I (TRI), which produces tropine (3α-hydroxytropane), and Tropinone Reductase II (TRII), which produces pseudotropine (3β-hydroxytropane) (Kushwaha et al., 2013). Tropine serves as the precursor for pharmacologically active alkaloids like hyoscyamine and scopolamine, while pseudotropine leads to the synthesis of calystegines. While TRs are not direct therapeutic targets for human diseases, they are of significant interest in biotechnology for the metabolic engineering of medicinal plants and microbes (Prashanth et al., 2018). Their structural characteristics have been extensively studied to understand how subtle changes in the active site determine the stereochemical outcome of the reaction (Yamada et al., 2003). Consequently, they serve as important tools for the industrial production of anticholinergic and anesthetic compounds.

Other names

Tropinone:NADPH oxidoreductaseTropine-forming tropinone reductasePseudotropine-forming tropinone reductaseTRITRII

Catalyzes the NADPH-dependent reduction of the 3-keto group of tropinone to either the 3-alpha (tropine) or 3-beta (pseudotropine) alcohol isomer.