Biosynthesis of cholesterol and steroids

The conversion of HMG-CoA to mevalonate by HMG-CoA reductase is the rate-limiting step of cholesterol biosynthesis and is under strict regulatory control (see Figure 1 ). HMGR is the target of compounds that are effective in lowering serum cholesterol levels. Human HMG-CoA reductase consists of a single polypeptide chain of 888 amino acids. The amino-terminal residues are membrane bound and reside in the endoplasmic reticulum membrane, while the catalytic site of the protein resides in its cytoplasmic, soluble carboxy-terminal portion. A linker region connects the two portions of the protein.

From a dietary perspective, plant cells do not manufacture cholesterol, and it is not found in plant foods. [30] [32] Some plant foods, such as avocado , flax seeds and peanuts , contain phytosterols , which compete with cholesterol for absorption in the intestines, reducing the absorption of both dietary and bile cholesterol. [33] However, a typical diet contributes on the order of grams of phytosterols, which is not enough to have a significant impact on blocking cholesterol absorption. Phytosterols intake can be supplemented through the use of phytosterol-containing functional foods or dietary supplements that are recognized as having potential to reduce levels of LDL -cholesterol. [34] Some supplemental guidelines have recommended doses of phytosterols in the – grams per day range (Health Canada, EFSA, ATP III, FDA). A recent meta-analysis demonstrating a 12% reduction in LDL-cholesterol at a mean dose of  grams per day. [35] However, the benefits of a diet supplemented with phytosterols have been questioned. [36]

Biosynthesis of cholesterol and steroids

biosynthesis of cholesterol and steroids


biosynthesis of cholesterol and steroidsbiosynthesis of cholesterol and steroidsbiosynthesis of cholesterol and steroidsbiosynthesis of cholesterol and steroidsbiosynthesis of cholesterol and steroids