CYP11A1

Cholesterol side-chain cleavage enzyme is commonly referred to as P450scc, where "scc" is an acronym for side-chain cleavage. P450scc is a mitochondrial enzyme that catalyzes conversion of cholesterol to pregnenolone. This is the first reaction in the process of steroidogenesis in all mammalian tissues that specialize in the production of various steroid hormones. P450scc is a member of the cytochrome P450 superfamily of enzymes (family 11, subfamily A, polypeptide 1). The gene name is CYP11A1. The highest level of the cholesterol side-chain cleavage system is found in the adrenal cortex and the corpus luteum. The system is also expressed at high levels in steroidogenic theca cells in the ovary, and Leydig cells in the testis. In each steroidogenic cell, the expression of the P450scc system proteins is regulated by the trophic hormonal system specific for the cell type. In adrenal cortex cells from zona fasciculata, the expression of the mRNAs encoding all three P450scc proteins is induced by corticotropin (ACTH). The trophic hormones increase CYP11A1 gene expression through transcription factors such as steroidogenic factor 1 (SF-1), by the α isoform of activating protein 2 (AP-2) in the human, and many others. The production of this enzyme is inhibited notably by the nuclear receptor DAX-1.