| Abstrakt: |
The membrane-bound NAD+-dependent 3ß-hydroxy-steroid dehydrogenase/?5-?4-isomerase (3ß-HSD), located in the endoplasmic reticulum and in mitochondrial membrane (Luu-The et al.1989, 1990, Thomas et al.1989, Simard et al.1991a, Chapman et al.1992, Cherradi et al.1993, 1994, Sauer et al.1994), catalyzes the conversion of ?5-3ß-hydroxysteroids into the corresponding ?4-3-ketosteroids (Fig. 1). This activity is essential for the formation of all classes of steroids, namely, progesterone, mineralocorticoids, glucocorticoids, androgens and estrogens. In addition, the enzymes of the 3ß-HSD family also catalyze the formation and/or degradation of the 5a-androstanes and 5a-pregnanes, such as dihydrotestosterone (DHT) and dihydroprogesterone (Luu-The et al.1989, Rhéaume et al.1991, Simard et al.1991a, Zhao et al.1991, de Launoit et al.1992a,b, Mason 1993, Simard et al.1993a,b, Labrie et al.1994b, Sanchez et al.1994a). In human and rhesus monkey the 3ß-HSD activity is not only detectable in the adrenal |
