期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1993
卷号：90
期号：20
页码：9591-9595
DOI：10.1073/pnas.90.20.9591
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：In the biosynthetic pathway of tropane alkaloids, tropinone reductase (EC 1.1.1.236 ) (TR)-I and TR-II, respectively, reduce a common substrate, tropinone, stereospecifically to the stereoisomeric alkamines tropine and pseudotropine (psi-tropine). cDNA clones coding for TR-I and TR-II, as well as a structurally related cDNA clone with an unknown function, were isolated from the solanaceous plant Datura stramonium. The cDNA clones for TR-I and TR-II encode polypeptides containing 273 and 260 amino acids, respectively, and when these clones were expressed in Escherichia coli, the recombinant TRs showed the same strict stereospecificity as that observed for the native TRs that had been isolated from plants. The deduced amino acid sequences of the two clones showed an overall identity of 64% in 260-amino acid residues and also shared significant similarities with enzymes in the short-chain, nonmetal dehydrogenase family. Genomic DNA-blot analysis detected the TR-encoding genes in three tropane alkaloid-producing solanaceous species but did not detect them in tobacco. We discuss how the two TRs may have evolved to catalyze the opposite stereospecific reductions.
