DELTA-5-3-BETA-HYDROXYSTEROID DEHYDROGENASE DELTA-5-DELTA-4-KETOSTEROID ISOMERASE (3-BETA-HSD), A POSSIBLE ENZYME OF CARDIAC GLYCOSIDE BIOSYNTHESIS, IN CELL-CULTURES AND PLANTS OF DIGITALIS-LANATA EHRH

The in vitro transformation of pregnenolone into progesterone in Digitalis lanata tissues was shown to be catalyzed by a 3β-hydroxysteroid dehydrogenase/ketosteroid isomerase (3β-HSD). Product formation was monitored by HPLC. The enzyme could be partially characterized and 3β-HSD activities were measured in various Digitalis lanata tissues and in cell cultures of other plant species. Since no correlation was observed between biosynthetic competence of the tissue and 3β-HSD activity, it was concluded that this enzyme does not play a major role in regulating cardenolide biosynthesis. © 1990 Springer-Verlag.