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Aldosterone biosynthesis by a reconstituted cytochrome P-45011 beta system
Biochemical and Biophysical Research Communications
|February 29, 1984
Summary
Cytochrome P-450 11 beta catalyzes corticosterone conversion to aldosterone and 18-hydroxycorticosterone. Mitochondrial lipid extracts significantly enhance aldosterone production by this enzyme.
Area of Science:
- Biochemistry
- Endocrinology
- Molecular Biology
Background:
- Cytochrome P-450 11 beta is a key enzyme in steroidogenesis.
- The regulation of aldosterone synthesis is complex and not fully understood.
Purpose of the Study:
- To investigate the catalytic activity of purified cytochrome P-450 11 beta.
- To determine the effect of bovine adrenocortical mitochondrial lipid extracts on this activity.
Main Methods:
- Purification of cytochrome P-450 11 beta from bovine adrenocortical mitochondria.
- Incubation of [3H]corticosterone with the purified enzyme.
- Analysis of reaction products using high-performance liquid chromatography.
- Assay of aldosterone and 18-hydroxycorticosterone production rates.
- Assessment of the impact of lipidic extracts on enzymatic activity.
Main Results:
- Purified cytochrome P-450 11 beta produced aldosterone and 18-hydroxycorticosterone.
- Aldosterone production rate was 21.2 pmol/nmol P-450/min.
- 18-hydroxycorticosterone production rate was 1.17 nmol/nmol P-450/min.
- Lipidic extracts from zona glomerulosa mitochondria increased aldosterone production 28-fold.
- Lipidic extracts enhanced the conversion of 18-hydroxycorticosterone to aldosterone 4-fold.
Conclusions:
- Cytochrome P-450 11 beta possesses both 11 beta-hydroxylase and 18-hydroxylase activities.
- Mitochondrial lipidic factors significantly stimulate aldosterone biosynthesis, likely by enhancing the 18-hydroxylase activity of P-450 11 beta.