0000000000673622
AUTHOR
H. Ulrich Seitz
Plant progesterone 5β-reductase is not homologous to the animal enzyme. Molecular evolutionary characterization of P5βR from Digitalis purpurea
Plants of the genus Digitalis produce cardiac glycosides, i.e. digoxin, which are widely used for congestive heart failure. Progesterone 5beta-reductase (P5betaR) is a key enzyme in the biosynthesis of these natural products. Here, we have carried out the purification and partial amino acid sequencing of the native P5betaR from foxglove (Digitalis purpurea), and isolated a cDNA encoding this enzyme. Similarly to other steroid 5beta-reductases, the recombinant P5betaR catalyzes the stereospecific reduction of the Delta(4)-double bond of several steroids with a 3-oxo,Delta(4,5) structure. The gene encoding P5betaR is expressed in all plant organs, and maximally transcribed in leaves and matur…
Cloning and expression of two novel aldo-keto reductases fromDigitalis purpurealeaves
The aldo-keto reductase (AKR) superfamily comprises proteins that catalyse mainly the reduction of carbonyl groups or carbon–carbon double bonds of a wide variety of substrates including steroids. Such types of reactions have been proposed to occur in the biosynthetic pathway of the cardiac glycosides produced by Digitalis plants. Two cDNAs encoding leaf-specific AKR proteins (DpAR1 and DpAR2) were isolated from a D. purpurea cDNA library using the rat Δ4-3-ketosteroid 5β-reductase clone. Both cDNAs encode 315 amino acid proteins showing 98.4% identity. DpAR proteins present high identities (68–80%) with four Arabidopsis clones and a 67% identity with the aldose/aldehyde reductase from Medi…
LC-NMR applied to the characterisation of cardiac glycosides from three micropropagatedIsoplexisspecies
Species of the genus Isoplexis are of particular interest with respect to the biochemical pathway leading to the cardenolides. It is important to determine whether or not 5β-configured compounds, typically produced by Digitalis species and used in medicine, are present together with their respective α-isomers in Isoplexis spp. Structure elucidation by LC-NMR of the products isolated from in vitro regenerated Isoplexis canariensis, I. chalcantha and I. isabelliana was carried out, and similarities were observed among the products of the three species, including the presence of digitoxigenin-type cardenolides in I. canariensis and xysmalogenin and canarigenin derivatives in I. chalcantha neve…