Cholesterol steroid pathway

Many abusers who inject anabolic steroids may use nonsterile injection techniques or share contaminated needles with other abusers. In addition, some steroid preparations are manufactured illegally under nonsterile conditions. These factors put abusers at risk for acquiring lifethreatening viral infections, such as HIV and hepatitis B and C. Abusers also can develop endocarditis, a bacterial infection that causes a potentially fatal inflammation of the inner lining of the heart. Bacterial infections also can cause pain and abscess formation at injection sites.

Biosynthesis of steroid hormones requires a battery of oxidative enzymes located in both mitochondria and endoplasmic reticulum. The rate-limiting step in this process is the transport of free cholesterol from the cytoplasm into mitochondria. Within mitochondria, cholesterol is converted to pregnenolone by an enzyme in the inner membrane called CYP11A1. Pregnenolone itself is not a hormone, but is the immediate precursor for the synthesis of all of the steroid hormones. The following table delineates the enzymes required to synthesize the major classes of steroid hormones.

Cholesterol synthesis
(KEGG pathway MAP00100 ) While dietary cholesterol uptake in humans is limited to about /day or less, all physiological requirments for cholesterol are supplied by the liver through de novo synthesis of cholesterol from acetyl-CoA. Cholesterol, a C27 compound is synthesized in a pathway that can be split in three parts: 1. Synthesis of mevalonate, a reduced C6 compound from 3 Acetyl-CoA units
2. Activation of mevalonate to isopentenyl-PP (isoprene unit), a C5 precursor which is used to elongate a lipid chain to squalene, a C30 intermediate
3. Cyclycation and demethylation of squalene by monooxygenases to the cyclic C27 cholesterol end product

Cholesterol steroid pathway

cholesterol steroid pathway


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