Specific enzymes and cofactors are required for glucocorticoid and androgen biosynthesis. These enzymes are located either in the smooth endoplasmic reticulum or in the mitochondria within each cell. Movement of substrate between these organelles is therefore necessary, and this mechanism of intracellular transport may require specific steroid-binding proteins. Thus, intracellular feedback effects of intermediates in the earlier biosynthetic steps may be of importance in regulating cholesterol biosynthesis.
