Figure 601

Metabolic pathways of corticosteroid biosynthesis.

proceeds from 17a-hydroxyprogesterone and 1-deoxy-cortisol to yield cortisol. Thus, steroid intermediates are converted to steroid end products by sequential 17-, 21-, and 11-hydroxylation reactions. 11-p-Hydroxylation is essential for glucocorticoid and mineralocorticoid activity of a steroid. The steroid hydroxylase system has the characteristics of a mixed-function oxidase, since two substrates, steroid and NADPH, are oxidized. All hydroxylases seem to be associated with a specific cytochrome P450.

The 17- and 21-hydroxylase enzymes are associated with microsomes, whereas the 11-p-hydroxylase has a mitochondrial origin. Since the last-named enzyme is not detectable in other steroid-producing tissues, the term 11-oxygenated steroids is considered synonymous with adrenal steroids. Aldosterone synthesis involves an essential 18-hydroxylation step catalyzed by P450c18 with corticosterone as the precursor; this reaction also takes place within the mitochondria.

Blood Pressure Health

Blood Pressure Health

Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...

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