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. Author manuscript; available in PMC: 2010 Jan 27.
Published in final edited form as: Vet Pathol. 2009 Mar;46(2):194–210. doi: 10.1354/vp.46-2-194

Fig. 1.

Fig. 1

Steroid hormone biosynthetic pathways. All steroidogenic cells share the capacity to mobilize and cleave cholesterol. The repertoire of enzymes distal to P450scc determines the steroidogenic capacity of a given cell. Note that P450c17 has both 17α-hydroxylase and 17,20-lyase activities. Cyt b5 selectively enhances the 17,20-lyase activity of P450c17 through allosteric effects. Abbreviations: 3β-HSD, 3β-hydroxysteroid dehydrogenase; 17β-HSD, 17β-hydroxysteroid dehydrogenase; cyt b5, cytochrome b5; DOC, deoxycorticosterone; DHEA, dehydroepiandrosterone; P450aldo, aldosterone synthase; P450c11, cytochrome P450 11β-hydroxylase; P450c17, cytochrome P450 17α-hydroxylase/17,20-lyase; P450c21, cytochrome P450 21-hydroxylase.