Rate limiting enzyme in cholesterol synthesis is:: (A) HMG -CoA reductase, (B) HMG -CoA synthetase, (C) HMG CoA lyase, (D) Mevalonate synthetase
Answer is A. Hydroxymethylglutaryl-coenzyme A (HMG-CoA) is the precursor for cholesterol synthesis.HMG-CoA is also an intermediate on the pathway for synthesis of ketone bodies from acetyl-CoA.The enzymes for ketone body production are located in the mitochondrial matrix.HMG-CoA destined for cholesterol synthesis is made by equivalent, but different, enzymes in the cytosol. HMG-CoA is formed by condensation of acetyl-CoA and acetoacetyl-CoA, catalyzed by HMG-CoA Synthase.HMG-CoA Reductase is an integral protein of endoplasmic reticulum membranes. The catalytic domain of this enzyme remains active following cleavage from the transmembrane poion of the enzyme.The HMG-CoA Reductase reaction is rate-limiting for cholesterol synthesis