Polyclonal antibodies raised against 3β-hydroxysteroid dehydrogenase isolated from human placenta were used to screen a λgt11 expression cDNA library from the same tissue. The protein deduced from cDNA sequences contains 372 amino acids with a calculated mol wt of 42,216. Since 3β-hydroxysteroid dehydrogenase is the enzyme catalyzing the formation of all classes of hormonal steroids, the availability of the cDNA encoding this enzyme opens new possibilities for a detailed investigation of the factors regulating the expression and activity of this crucial enzyme in adrenal, gonadal as well as peripheral tissues. The formation of Δ4-3-keto steroids from Δ5-ene, 3β-hydroxy precursors is a key step in the biosynthesis of all classes of hormonal steroids, namely glucocorticoids, mineralocorticoids, progesterone, androgens, and estrogens. This reaction is catalyzed by the enzymatic system 3β-hydroxy-5-ene-steroid dehydrogenase (EC 1.1.1.145) and steroid Δ5-Δ4-ene-isomerase (EC-5.3.3.1), hereafter called 3β-HSD (1). The 3β-HSD enzymatic system is present in the adrenals, testes, ovaries, and placenta as well as in many peripheral tissues including the prostate, breast, liver and skin (2–4). Congenital deficiency of 3β-HSD activity causes severe depletion of steroid formation by the adrenals and gonads and is usually lethal in early life (5).
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The et al. (1989) studied this question.