Postsqualene cholesterol synthetic pathway

Postsqualene cholesterol synthetic pathway. This figure depicts the postsqualene cholesterol synthetic pathway. Lanosterol is the first sterol formed after cyclization of squalene. Lanosterol is converted to cholesterol in a series of enzymatic reactions. Two major synthetic pathways exist, primarily distinguished by the timing of the reduction of the Δ24-bond in the aliphatic side chain by sterol Δ24-reductase. If reduction of the Δ24-bond occurs early, cholesterol is synthesized via the Kandutsch-Russel pathway (right side of the figure). This pathway appears to be favored in most tissues. In the Bloch pathway (left side of the figure) reduction of the Δ24-bond occurs as the last enzymatic step that converts desmosterol to cholesterol. Significant levels of desmosterol are found in the developing brain. The enzyme names and the corresponding genes are in italics (small and large type, respectively). *The C-4 demethylation complex consists of three proteins (NSHDL, sterol C-4 methyloxidase, and 3β-ketosterol reductase). Syndromes associated with defects at specific steps are indicated in red, bold type, genes in green, and enzymes in blue. HEM dysplasia and Antley-Bixler syndrome are in parentheses to indicate that they are not simply due to disruption of the corresponding enzymatic reaction. 7DHC is a precursor for both cholesterol and Vitamin D. In skin tissue photolysis of 7DHC in the skin leads to the formation of previtamin D3.

Publication

Malformation syndromes caused by disorders of cholesterol synthesis. (2011) Forbes D. Porter, et al. J Lipid Res. 2011 Jan;52(1):6-34. Figure: F2. All organisms Danio rerio Homo sapiens

Disease mentions