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The cytosolic acetyl-CoA can also condense with acetoacetyl-CoA to form 3-hydroxy-3-methylglutaryl-CoA which is the rate-limiting step controlling the synthesis of cholesterol. [16] Cholesterol can be used as is, as a structural component of cellular membranes, or it can be used to synthesize steroid hormones , bile salts , and vitamin D .
Coenzyme A (CoA, SHCoA, CoASH) is a coenzyme, notable for its role in the synthesis and oxidation of fatty acids, and the oxidation of pyruvate in the citric acid cycle.All genomes sequenced to date encode enzymes that use coenzyme A as a substrate, and around 4% of cellular enzymes use it (or a thioester) as a substrate.
HMG-CoA synthase: Acetoacetyl-CoA condenses with another Acetyl-CoA molecule to form 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA). HMG-CoA reductase: HMG-CoA is reduced to mevalonate by NADPH. This is the rate limiting step in cholesterol synthesis, which is why this enzyme is a good target for pharmaceuticals . mevalonate-5-kinase
The synthesis of even-chained fatty acid synthesis is done by assembling acetyl-CoA precursors, however, propionyl-CoA instead of acetyl-CoA is used as the primer for the biosynthesis of long-chain fatty acids with an odd number of carbon atoms. [19] Regulation. In B. subtilis, this pathway is regulated by a two-component system: DesK and DesR.
It begins with acetyl-CoA and involves the stepwise condensation of two-carbon units, typically derived from malonyl-CoA, to form increasingly longer carbon chains. In fatty acid synthesis, these chains are fully reduced after each elongation step, while in polyketide synthesis, the reduction steps may be partially or completely omitted ...
Acetyl Co-A can also be used in fatty acid synthesis, and a common function of the synthetase is to produce acetyl Co-A for this purpose. [3] The reaction catalyzed by acetyl-CoA synthetase takes place in two steps. First, AMP must be bound by the enzyme to cause a conformational change in the active site, which allows the reaction to take place.
The cytosolic acetyl-CoA can be carboxylated by acetyl-CoA carboxylase into malonyl CoA, the first committed step in the synthesis of fatty acids, or it can be combined with acetoacetyl-CoA to form 3-hydroxy-3-methylglutaryl-CoA which is the rate limiting step controlling the synthesis of cholesterol. [47]
Acetoacetyl CoA is the precursor of HMG-CoA in the mevalonate pathway, which is essential for cholesterol biosynthesis. It also takes a similar role in the ketone bodies synthesis (ketogenesis) pathway of the liver. [1] In the ketone bodies digestion pathway (in the tissue), it is no longer associated with having HMG-CoA as a product or as a ...