20beta-hydroxy-C21-steroid 20beta-oxidase activity of cytochrome P450c21 purified from bovine adrenocortical microsomes.
Biochim Biophys Acta
; 1390(2): 197-206, 1998 Feb 16.
Article
in En
| MEDLINE
| ID: mdl-9507127
ABSTRACT
We showed previously that cytochrome P450c21 (CYP21A1) from bovine adrenocortical microsomes has a putative 20beta-oxidase activity for 20beta-hydroxyprogesterone leading to a conversion to progesterone [M. Tsubaki, K. Morimoto, S. Tomita, S. Miura, Y. Ichikawa, A. Miyatake, F. Masuya, H. Hori, Biochim. Biophys. Acta 1259 (1995) 89-98]. We have extended the investigation on the 20beta-oxidase activity of cytochrome P450c21. Combination of 17alpha, 20beta-dihydroxyprogesterone with purified cytochrome P450c21 in oxidized form caused an induction of a typical type I difference spectrum (a peak at 390 nm and a trough at 420 nm) with a spectral dissociation constant of 2.3 microM. EPR spectrum at low temperature (15 K) exhibited an appearance of a new low-spin signal at gz=2.42, gy=2.21, and gx=1.966 and an increase in intensity of the high-spin signal (g=8.06, 3.54) upon formation of the enzyme-steroid complex, as previously found for 17alpha-hydroxyprogesterone and 20beta-hydroxyprogesterone. The enzymatic activity for 17alpha, 20beta-dihydroxyprogesterone was confirmed in a reconstituted system consisting of cytochrome P450c21 and NADPH-cytochrome P450 reductase. 17alpha,20beta-Dihydroxyprogesterone was converted to 17alpha-hydroxyprogesterone via the 20beta-oxidase reaction. The high turnover numbers of the 20beta-oxidase activity for 20beta-hydroxy-c21-steroids suggests that this activity is likely to have some physiological roles. Cytochrome P450c21 and 20beta-hydroxysteroid dehydrogenase may regulate the androgen biosynthesis catalyzed by cytochrome P450c17alpha with controlling the concentration of 20beta-hydroxy-C21-steroids.
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Collection:
01-internacional
Database:
MEDLINE
Main subject:
Adrenal Glands
/
Cytochrome P-450 Enzyme System
/
Microsomes
Limits:
Animals
Language:
En
Journal:
Biochim Biophys Acta
Year:
1998
Document type:
Article
Affiliation country: