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CoA is acetylated to acetyl-CoA by the breakdown of carbohydrates through glycolysis and by the breakdown of fatty acids through β-oxidation. Acetyl-CoA then enters the citric acid cycle, where the acetyl group is oxidized to carbon dioxide and water, and the energy released is captured in the form of 11 ATP and one GTP per acetyl group.
However, if the amounts of acetyl-CoA generated in fatty-acid β-oxidation challenge the processing capacity of the TCA cycle; i.e. if activity in TCA cycle is low due to low amounts of intermediates such as oxaloacetate, acetyl-CoA is then used instead in biosynthesis of ketone bodies via acetoacetyl-CoA and β-hydroxy-β-methylglutaryl-CoA .
Fatty acid degradation is the process in which fatty acids are broken down into their metabolites, in the end generating acetyl-CoA, the entry molecule for the citric acid cycle, the main energy supply of living organisms, including bacteria and animals. [1] [2] It includes three major steps: Lipolysis of and release from adipose tissue
The succinyl-CoA formed then enters the citric acid cycle. However, whereas acetyl-CoA enters the citric acid cycle by condensing with an existing molecule of oxaloacetate, succinyl-CoA enters the cycle as a principal in its own right. Thus, the succinate just adds to the population of circulating molecules in the cycle and undergoes no net ...
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 ...
The role of the ACS enzyme is to combine acetate and Coenzyme A to form acetyl-CoA, however its significance is much larger. The most well known function of the product from this enzymatic reaction is the use of acetyl-CoA in the role of the TCA cycle as well as in the production of fatty acid.
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]
General chemical structure of an acyl-CoA, where R is a carboxylic acid side chain. Acyl-CoA is a group of CoA-based coenzymes that metabolize carboxylic acids. Fatty acyl-CoA's are susceptible to beta oxidation, forming, ultimately, acetyl-CoA. The acetyl-CoA enters the citric acid cycle, eventually forming several equivalents of ATP. In this ...