Pregnenolone biosynthesis

Stable Identifier
R-HSA-196108
Type
Pathway
Species
Homo sapiens
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The first process in the synthesis of all steroid hormones is the synthesis of pregnenolone from cholesterol. In this process, cholesterol mobilized from cytosolic lipid droplets or from lysosomes is transported to mitochondria and becomes localized to the inner mitochondrial membrane. Cholesterol transport appears to be rate-limiting for steroid hormone synthesis and its regulation, at the step of StAR-mediated traversal of the mitochondrial membrane, plays a central role in determining the amounts and identities of steroid hormones made in the body. In the inner mitochondrial membrane, cholesterol is converted to pregnenolone in a sequence of three reactions, all catalyzed by CYP11A (side chain cleavage enzyme). Finally, pregnenolone re-enters the cytosol (Payne and Hales 2004; Stocco 2001).

Literature References
PubMed ID Title Journal Year
15583024 Overview of steroidogenic enzymes in the pathway from cholesterol to active steroid hormones

Payne, AH, Hales, DB

Endocr Rev 2004
11181954 StAR protein and the regulation of steroid hormone biosynthesis

Stocco, DM

Annu Rev Physiol 2001
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