HMG CoA Reductase

HMG‐CoA reductase is the committed and therefore the regulatory step in cholesterol biosynthesis. If HMG‐CoA is reduced to mevalonate, cholesterol is the only product that can result. The reduction is a two‐step reaction, which releases the Coenzyme A cofactor and converts the thiol‐bound carboxylic group of HMG‐CoA to a free alcohol. Two NADPH molecules supply the reducing equivalents because the thioester must first be reduced to the level of an aldehyde and then to an alcohol.