kolesterolszintézis

Kolesterolszintézis refers to the biological process by which living organisms produce cholesterol. This complex metabolic pathway is essential for the synthesis of cell membranes, steroid hormones, bile acids, and vitamin D. The primary site of cholesterol synthesis in mammals is the liver, although most nucleated cells also possess the capability to produce cholesterol. The process begins with the formation of acetyl-CoA, which is then converted into mevalonate through a series of enzymatic reactions. This rate-limiting step is catalyzed by HMG-CoA reductase. From mevalonate, the pathway proceeds through isoprenoid intermediates to form squalene, which is then cyclized and modified to yield cholesterol. Regulation of cholesterol synthesis is tightly controlled, primarily by the intracellular cholesterol concentration. High levels of cholesterol inhibit the activity of HMG-CoA reductase and reduce the synthesis of the enzyme, thereby downregulating the pathway. Conversely, low cholesterol levels stimulate HMG-CoA reductase activity. Genetic defects in the enzymes involved in cholesterol synthesis can lead to severe metabolic disorders. Many pharmaceuticals, such as statins, target this pathway by inhibiting HMG-CoA reductase, thereby lowering blood cholesterol levels.