How is biosynthesis of cortisol compartmentalized and regulated within the cell?

 

ACTH increases the expression of both StAR and P450scc in cell of the zona fasciculata and zona recticularis. Thus under ACTH stimulation, the zones of the adrenal cortex take up cholesterol and convert it to pregnenolone. Pregnenolone is converted to 17-hydroxy-pregnenolone by P450c17, which is localized in the membrane of the smooth endoplasmic reticulum.

Another enzyme in the SER, 3 beta HSD, converts 17-hydroxy-pregnenolone to 17-hydroxy-progesterone, which then is converted by another enzyme of the SER, P450c 21, to 11-deoxy-cortisol. 11-deoxycortisol diffuses out of the SER, and into the mitochondria where the P450c11 converts it to cortisol. Cortisol then diffuses out of the cell.