Pregnane and Allopregnane Derivatives

Progesterone is the precursor of hydroxylated pregnane derivatives of the cortisone and aldosterone types (Fig. 129). In this transformation monooxygenases (C 2.6.4) and dehydrogenases (C 2.1) are involved. In animals the hydroxylated pregnenes undergo a rapid turnover (A 5.2). Transformation takes 

1 Monooxygenases 2 20a,22R-dihydroxycholesterol aldolase 3 3-j -hydroxy-Zl -steroid dehydrogenase, steroid-zl-isomerase 

1 Steroid 17(X-monooxygenase 2 steroid 21-monooxygenase 3 steroid 11 -monooxygenase 4 dehydrogenase 5 corticosterone 18-monooxygenase, steroid 18-oxidase 

Progesterone, cortisol, cortisone, aldosterone and related compounds have hormone activity in animals (E 3.1). Progesterone regulates the metabolic activity of the gonads. It is synthesized mainly in the corpus luteum and the placenta. Cortisol, cortisone, and aldosterone influence carbohydrate and mineral metabolism. They are formed in the adrenal cortex (corticosteroids), but also in the gonads and the placenta. All compounds mentioned are used in medicine (F 2) and are produced by the pharmaceutical industry, e.g., from steroid saponins (D 6.4.2) or steroid alkaloids (D 6.4.3). 

Cortexone and 12-hydroxy-4,6-pregnadien-3,20-dione are feeding deterrents of certain water beetles (E 5.1). They act as hormones in vertebrate predators. 

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The biochemical reduction of the C20 ketone in human subjects seems to be stereospecifically directed to the 20a-hydroxyl group. Of the eight possible 3,20-dihydroxy derivatives of pregnane and allopregnane, only those with the a configuration at Csc have been isolated from human... 

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