This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Hashimoto, T. Articles by Yamada, Y. Search for Related Content PubMed PubMed Citation Articles by Hashimoto, T. Articles by Yamada, Y. Agricola Articles by Hashimoto, T. Articles by Yamada, Y.

Metabolism and Enzymology

Two Tropinone Reductases with Distinct Stereospecificities from Cultured Roots of Hyoscyamus niger¹

Department of Agricultural Chemistry, Faculty of Agriculture, Kyoto University, Kyoto 606, Japan

Tropinone is an alkamine intermediate at the branch point of biosynthetic pathways leading to various tropane alkaloids. Two stereospecifically distinct NADPH-dependent oxidoreductases, TR-I and TR-II, which, respectively, reduce tropinone to 3-hydroxytropane (tropine) and 3-hydroxytropane (-tropine), were detected mainly in the root of tropane alkaloid-producing plants but not in nonproducing cultured root. Both reductases were purified to near homogeneity from cultured root of Hyoscyamus niger and characterized. The TR-I reaction was reversible, whereas the TR-II reaction was essentially irreversible, reduction of the ketone being highly favored over oxidation of the alcohol -tropine. Marked differences were found between the two reductase in their affinities for tropinone substrate and in the effects of amino acid modification reagents. Some differences in substrate specificity were apparent. For example, N-propyl-4-piperidone was reduced by TR-II but not by TR-I. Conversely, 3-quinuclidinone and 8-thiabicyclo[3,2,1]octane-3-one were accepted as substrates by TR-I but hardly at all by TR-II. Both enzymes were shown to be class B oxidoreductases, which transfer the pro-S hydrogen of NAD(P)H to their substrates. Possible roles of these tropinone reductases in alkaloid biosynthesis are discussed.

¹ This work was supported in part by a grant from the Ministry of Education, Science, and Culture of Japan (No. 2660090 to T.H.).

This article has been cited by other articles:

				U. Richter, G. Rothe, A.-K. Fabian, B. Rahfeld, and B. Drager Overexpression of tropinone reductases alters alkaloid composition in Atropa belladonna root cultures J. Exp. Bot., February 1, 2005; 56(412): 645 - 652. [Abstract] [Full Text] [PDF]

				L. Zhang, R. Ding, Y. Chai, M. Bonfill, E. Moyano, K.-M. Oksman-Caldentey, T. Xu, Y. Pi, Z. Wang, H. Zhang, et al. Engineering tropane biosynthetic pathway in Hyoscyamus niger hairy root cultures PNAS, April 27, 2004; 101(17): 6786 - 6791. [Abstract] [Full Text] [PDF]

				S. Sogabe, A. Yoshizumi, T. A. Fukami, Y. Shiratori, S. Shimizu, H. Takagi, S. Nakamori, and M. Wada The Crystal Structure and Stereospecificity of Levodione Reductase from Corynebacterium aquaticum M-13 J. Biol. Chem., May 23, 2003; 278(21): 19387 - 19395. [Abstract] [Full Text] [PDF]

				K. Nakajima, H. Kato, J.'i. Oda, Y. Yamada, and T. Hashimoto Site-directed Mutagenesis of Putative Substrate-binding Residues Reveals a Mechanism Controlling the Different Stereospecificities of Two Tropinone Reductases J. Biol. Chem., June 4, 1999; 274(23): 16563 - 16568. [Abstract] [Full Text] [PDF]

				K. Nakajima, A. Yamashita, H. Akama, T. Nakatsu, H. Kato, T. Hashimoto, J.'i. Oda, and Y. Yamada Crystal structures of two tropinone reductases: Different reaction stereospecificities in the same protein fold PNAS, April 28, 1998; 95(9): 4876 - 4881. [Abstract] [Full Text] [PDF]

				F. Sato, T. Hashimoto, A. Hachiya, K.-i. Tamura, K.-B. Choi, T. Morishige, H. Fujimoto, and Y. Yamada Inaugural Article: Metabolic engineering of plant alkaloid biosynthesis PNAS, January 2, 2001; 98(1): 367 - 372. [Abstract] [Full Text] [PDF]