| | 1 | Author
| HildegardM. Aria, W. Arneck, H. Anns, Ulrich Seitz | Requires cookie* | | | Title
| 3 ß-Hydroxysteroid Oxidoreductase in Suspension Cultures of Digitalis lanata EH RH  | | | | Abstract
| A 3 ß-hydroxysteroid oxidoreductase was isolated and characterized in the m icrosomes o f Digitalis lanata cell cultures. The enzyme catalyzes the conversion o f 5a-pregnane-3,20-dione to 5a-pregnan-3 ß-ol-20-one and requires N A D (P)H 2. The enzyme was found to have a pH optimum o f 8.0. The reaction had an optimum incubation temperature o f 25 °C with linear reduction for the first 4 h, reaching maximum enzyme activity after 7 h. Substrate kinetics for 5a-pregnane-3,20-dione and N A D P H 2 resulted in apparent A^-values o f 1 8 .5 -2 0 (iM for 5a-pregnane-3,20-dione and 5 0 -1 2 0 |iM for the co-substrate N A D P H ,. In order to localize 3 ß-hydroxysteroid oxidoreductase differential centrifugation as well as linear sucrose density gradient centrifugation were performed. The results obtained lead to the conclusion that 3 ß-hydroxysteroid oxidoreductase is not associated with a single cell compartment, but con sists o f a major soluble part and a markedly smaller part o f endoplasmic reticulum-associated activity. | | | |
Reference
| Z. Naturforsch. 45c, 963 (1990); received July 16. 1990 | | | |
Published
| 1990 | | | |
Keywords
| Cell Cultures, Digitalis lanata, 3 ß-Hydroxysteroid Oxidoreductase, Steroids | | | |
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| default:Reihe_C/45/ZNC-1990-45c-0963.pdf | | | | Identifier
| ZNC-1990-45c-0963 | | | | Volume
| 45 | |
| 2 | Author
| Maike Petersen, Ulrich Hanns, Seitz, Ernst Reinhard | Requires cookie* | | | Title
| Characterization and Localization of Digitoxin 12 ß-Hydroxylase from Cell Cultures of Digitalis lanata EHRH | | | | Abstract
| The cytochrome P-450-dependent monooxygenase digitoxin 12ß-hydroxylase from cell cultures of Digitalis lanata needs NADPH and molecular oxygen and hydroxylates cardiac glycosides with the aglycon of digitoxigenin to the corresponding derivatives of the C-series. Other electron donors cannot replace NADPH. The apparent K" m -values are 26 UM for NADPH, 7.1 ^IM for ß-methyldigitoxin and 10 ^IM for digitoxin. The reaction is inhibited by NADP + and cytochrome c in a competitive mode. The optimum temperature was at 20 °C. Low concentrations of Mn 2+ , Mg 2+ , and EDTA were slightly stimulatory, but there was no strict dependence on divalent cations. Digitoxin 12ß-hydroxylase is very stable at room temperature and the reaction proceeds for more than 20 h. After the addition of 15% glycerol, 70% of the original activity can be retained subsequent to freezing at —18 °C. By means of linear sucrose gradient fractionation of cellular membranes the digitoxin 12ß-hydroxylase was found to be located in the endoplasmic reticulum. | | | |
Reference
| Z. Naturforsch. 43c, 199—206 (1988); received December 8 1987 | | | |
Published
| 1988 | | | |
Keywords
| Cardiac Glycosides, Cytochrome P-450, Digitalis lanata, Digitoxin 12ß-Hydroxylase, Endoplas-mic Reticulum | | | |
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| default:Reihe_C/43/ZNC-1988-43c-0199.pdf | | | | Identifier
| ZNC-1988-43c-0199 | | | | Volume
| 43 | |
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