Progesterone: Its Possible Role in the Biosynthesis of Cardenolides in
            <i>Digitalis lanata</i>

Caspi, Eliahu; Lewis, D. O.

doi:10.1126/science.156.3774.519

Cited by 55 publications

(18 citation statements)

References 15 publications

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“…This observation is somewhat striking since A4-pregnenes are generally assumed to be more direct precursors of cardenolides than A5-pregnenes. However, Caspi and Lewis (29) found earlier that cortexone is only a poor precursor of cardenolides. Generally, compounds showing the pregnenolone structure were incorporated into cardenolides at a much higher rate than the respective progesterone-type precursors or even the 5/3-configurated pregnanes (see below).…”

Section: Tissue Culturesmentioning

confidence: 97%

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Effects of Various Pregnanes and Two 23-Nor-5-cholenic Acids on Cardenolide Accumulation in Cell and Organ Cultures ofDigitalis lanata

et al. 1997

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5-Pregnen-3beta-ol-20-one (pregnenolone), 4-pregnene-3,20-dione (progesterone), 5-pregnene-3beta,21-diol-20-one (21-hydroxypregnenolone), 4-pregnen-21 -ol-3,20-dione (cortexone), 5beta-pregnane-3,20-dione, 5alpha-pregnane-3,20-dione, 5beta-pregnan-3alpha-ol-20-one, 5beta-pregnan-3beta-ol-20-one, 5beta-pregnane-3beta,14beta, 21-triol-20-one 3-acetate, 23-nor-5-cholenic acid-3beta,20xi-diol, and 23-nor-3,20(22) E-choladienic acid-3beta-ol were administered to photomixotrophic shoot cultures of Digitalis lanata Ehrh. capable of synthesizing cardenolides, as well as to cardenolide-free tissue cultures, such as auxotrophic, dark-grown shoot cultures and cell suspension cultures of the same plant species. None of the pregnane precursors was qualified to restore cardenolide biosynthesis in the cardenolide-free tissues. The cardenolide content of light-grown shoot cultures, on the other hand, increased by 161%, 240%, 30%, 430% and 80% when 100 mg l(-1) of 21-hydroxypregnenolone, 5beta-pregnane-3,20-dione, 5beta-pregnan-3beta-ol-20-one, 5beta-pregnane-3beta,14beta,21-triol-20-one, 23-nor-5,20 (22) E-choladienic acid-3beta-ol, respectively, were administered. Pregnenolone, progesterone, cortexone, 5alpha-pregnanes, 5beta -pregnan-21-ols, and 23-nor-5-cholenic acid-3beta,20xi-diol, on the other hand, had no visible effect. Two different types of cardenolides (termed fucose-type cardenolides and digitoxose-type cardenolides) were identified which may be formed via different biosynthetic routes. The "norcholanic acid pathway" seems to be operative in D. lanata shoot cultures only in the formation of fucose-type cardenolides.

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Section: Tissue Culturesmentioning

confidence: 97%

“…The incubation time was 7 d.The different incorporation or stimulation rates seen in experiments where progesterone or pregnenolone were administered to either D. lanata plants (e.g., ref 29). or shoot cultures may be explained by the differences in the activities of preby: University of Illinois.…”

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confidence: 99%

Effects of Various Pregnanes and Two 23-Nor-5-cholenic Acids on Cardenolide Accumulation in Cell and Organ Cultures ofDigitalis lanata

et al. 1997

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“…Digitalis plants are still the major source for cardenolides, and as a step in the biosynthetic pathway, the Digitalis enzyme progesterone 5␤-reductase (5␤-POR) 2 catalyzes the stereospecific NADPH-dependent reduction of the ⌬ 4 -double bond in progesterone to 5␤-pregnane-3,20-dione. Because all Digitalis cardenolides share the characteristic 5␤-configuration, the enzyme 5␤-POR catalyzes a central step during their biosynthesis (5)(6)(7).…”

mentioning

confidence: 99%

The Crystal Structure of Progesterone 5β-Reductase from Digitalis lanata Defines a Novel Class of Short Chain Dehydrogenases/Reductases

Thorn

Egerer-Sieber

Jäger

et al. 2008

Journal of Biological Chemistry

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Progesterone 5␤-reductase (5␤-POR) catalyzes the stereospecific reduction of progesterone to 5␤-pregnane-3,20-dione and is a key enzyme in the biosynthetic pathway of cardenolides in Digitalis (foxglove) plants. Sequence considerations suggested that 5␤-POR is a member of the short chain dehydrogenase/reductase (SDR) family of proteins but at the same time revealed that the sequence motifs that in standard SDRs contain the catalytically important residues are missing. Here we present crystal structures of 5␤-POR from Digitalis lanata in complex with NADP ؉ at 2.3 Å and without cofactor bound at 2.4 Å resolution together with a model of a ternary complex consisting of 5␤-POR, NADP ؉ , and progesterone. Indeed, 5␤-POR displays the fold of an extended SDR. The architecture of the active site is, however, unprecedented because none of the standard catalytic residues are structurally conserved. A tyrosine (Tyr-179) and a lysine residue (Lys-147) are present in the active site, but they are displayed from novel positions and are part of novel sequence motifs. Mutating Tyr-179 to either alanine or phenylalanine completely abolishes the enzymatic activity. We propose that the distinct topology reflects the fact that 5␤-POR reduces a conjugated double bond in a steroid substrate via a 1-4 addition mechanism and that this requires a repositioning of the catalytically important residues. Our observation that the sequence motifs that line the active site are conserved in a number of bacterial and plant enzymes of yet unknown function leads us to the proposition that 5␤-POR defines a novel class of SDRs.The beneficial effects of cardenolides, also known as cardiac glycosides or cardiotonic steroids, are well documented, and they have been applied for the treatment of cardiac insufficiencies for centuries (1-3). On a molecular level, these steroids are potent inhibitors of the sodium/potassium pump (Na ϩ /K ϩ -ATPase) that is present in almost all cells in higher organisms (4). Digitalis plants are still the major source for cardenolides, and as a step in the biosynthetic pathway, the Digitalis enzyme progesterone 5␤-reductase (5␤-POR) 2 catalyzes the stereospecific NADPH-dependent reduction of the ⌬ 4 -double bond in progesterone to 5␤-pregnane-3,20-dione. Because all Digitalis cardenolides share the characteristic 5␤-configuration, the enzyme 5␤-POR catalyzes a central step during their biosynthesis (5-7).NADH/NADPH-dependent reductases as well as the related dehydrogenases, dehydratases, and epimerases can be classified into two major protein families: the (␣/␤) 8 -barrel containing aldo-keto-reductases (AKRs) (8) and the Rossman fold containing short chain dehydrogenases/reductases (SDRs) (9 -11). Additional families such as the long and medium chain dehydrogenases/reductases are related to SDRs because they share with the latter the dinucleotide-binding double Rossman fold (12)(13)(14). SDRs are about 250 residues long and form a large family with over 2000 members (15). Because their central feature consists of an all-p...

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“…Les syst6mes enzymatiques CtudiCs dans ce travail ont dCj& Ct C t~ouvCs chez plusieurs chordCs (30,32), certains microorganismes (321, et certaioes plantes (33). Ces syst6mes ont aussi Ct C dCcelCs chez les invertCbrCs soit l'huitre (11) et la limace (34) ; cependant, c'est la premi6re fois que leur prCsence est dCcelCe dam les tissus d 'insectes.…”

Section: Expe'riences P Et 2 Isolenlent Et Bd~rattj5catisn Deunclassified

L'oxydation de la prégnènolone en progestérone par des préparations de tissus des Orthoptères in vitro

LeHoux¹,

Chapdelaine²,

Sandor³

1970

Can. J. Biochem.

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Incubation of isotopically labelled pregnenolone with sliced testis tissue of adult Orthoptera (Gromphadorhina portentosa, Byrsotria fumigata, and Gryllus assimilis) in vitro has shown that these insect gonads are capable of transforming pregnenolone to progesterone. In addition, leg muscle preparations of Gryllus assimilis could also effect this transformation. In one of the experiments, pregnenolone gave rise to 20β-dihydroprogesterone. These studies demonstrated the presence of enzyme systems capable of oxidizing the steroidal 5-en-3β-ol function to 4-en-3-one structure in the three species investigated.

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Progesterone: Its Possible Role in the Biosynthesis of Cardenolides in Digitalis lanata

Cited by 55 publications

References 15 publications

Effects of Various Pregnanes and Two 23-Nor-5-cholenic Acids on Cardenolide Accumulation in Cell and Organ Cultures ofDigitalis lanata

Effects of Various Pregnanes and Two 23-Nor-5-cholenic Acids on Cardenolide Accumulation in Cell and Organ Cultures ofDigitalis lanata

The Crystal Structure of Progesterone 5β-Reductase from Digitalis lanata Defines a Novel Class of Short Chain Dehydrogenases/Reductases

L'oxydation de la prégnènolone en progestérone par des préparations de tissus des Orthoptères in vitro

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