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Aldosterone synthase, also called steroid 18-hydroxylase, corticosterone 18-monooxygenase or P450C18, is a steroid hydroxylase cytochrome P450 enzyme involved in the biosynthesis of the mineralocorticoid aldosterone and other steroids. The enzyme catalyzes sequential hydroxylations of the steroid angular methyl group at C18 after initial 11β ...
Aldosterone is the primary of several endogenous members of the class of mineralocorticoids in humans. [citation needed] Deoxycorticosterone is another important member of this class. Aldosterone tends to promote Na + and water retention, and lower plasma K + concentration by the following mechanisms:
18-Hydroxylase (aldosterone synthase) – mineralocorticoid synthesis; 21-Hydroxylase – corticosteroid synthesis; Cytochrome P450 (CYP1, 2, 3) – estrogen metabolism; Hydroxysteroid dehydrogenases (and ketosteroid reductases) 3α-Hydroxysteroid dehydrogenase – androgen, progestogen, and neurosteroid synthesis and metabolism
The name mineralocorticoid derives from early observations that these hormones were involved in the retention of sodium, a mineral.The primary endogenous mineralocorticoid is aldosterone, although a number of other endogenous hormones (including progesterone [1] and deoxycorticosterone) have mineralocorticoid function.
The outermost layer, the zona glomerulosa is the main site for the production of aldosterone, a mineralocorticoid. The synthesis and secretion of aldosterone are mainly regulated by the renin–angiotensin–aldosterone system. The zona glomerulosa cells express a specific enzyme aldosterone synthase (also known as CYP11B2).
In humans and other animals, the adrenocortical hormones are hormones produced by the adrenal cortex, the outer region of the adrenal gland.These polycyclic steroid hormones have a variety of roles that are crucial for the body's response to stress (for example, the fight-or-flight response), and they also regulate other functions in the body.
These enzymes are nearly identical (they share 11β-hydroxylation and 18-hydroxylation functions), but aldosterone synthase is also able to perform an 18-oxidation. Moreover, aldosterone synthase is found within the zona glomerulosa at the outer edge of the adrenal cortex ; 11β-hydroxylase is found in the zona fasciculata and zona glomerulosa .
Secondary hyperaldosteronism (also hyperreninism, or hyperreninemic hyperaldosteronism) is due to overactivity of the renin–angiotensin–aldosterone system (RAAS).. The causes of secondary hyperaldosteronism are accessory renal veins, fibromuscular dysplasia, reninoma, renal tubular acidosis, nutcracker syndrome, ectopic tumors, massive ascites, left ventricular failure, and cor pulmonale.