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At high glucose levels, acetyl-CoA is produced through glycolysis. [14] Pyruvate undergoes oxidative decarboxylation in which it loses its carboxyl group (as carbon dioxide) to form acetyl-CoA, giving off 33.5 kJ/mol of energy. The oxidative conversion of pyruvate into acetyl-CoA is referred to as the pyruvate dehydrogenase reaction.
In biochemistry and metabolism, beta oxidation (also β-oxidation) is the catabolic process by which fatty acid molecules are broken down in the cytosol in prokaryotes and in the mitochondria in eukaryotes to generate acetyl-CoA. Acetyl-CoA enters the citric acid cycle, generating NADH and FADH 2, which are electron carriers used in the ...
Acetyl-CoA synthetase is also produced when it is needed for fatty acid synthesis, but, under normal conditions, the gene is inactive and has certain transcriptional factors that activate transcription when necessary. [3] In addition to sirtuins, protein deacetylase (AcuC) also can modify acetyl-CoA synthetase at a lysine residue.
This cannot occur directly. To obtain cytosolic acetyl-CoA, citrate (produced by the condensation of acetyl-CoA with oxaloacetate) is removed from the citric acid cycle and carried across the inner mitochondrial membrane into the cytosol. [7] There it is cleaved by ATP citrate lyase into acetyl-CoA and oxaloacetate.
Instead the acetyl-CoA produced by the beta-oxidation of fatty acids condenses with oxaloacetate, to enter the citric acid cycle. During each turn of the cycle, two carbon atoms leave the cycle as CO 2 in the decarboxylation reactions catalyzed by isocitrate dehydrogenase and alpha-ketoglutarate dehydrogenase. Thus each turn of the citric acid ...
Ketone bodies are water-soluble molecules or compounds that contain the ketone groups produced from fatty acids by the liver (ketogenesis). [1] [2] Ketone bodies are readily transported into tissues outside the liver, where they are converted into acetyl-CoA (acetyl-Coenzyme A) – which then enters the citric acid cycle (Krebs cycle) and is oxidized for energy.
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 .
Cytosolic citrate, meaning citrate in the cytosol, is a key substrate for the generation of energy. It releases acetyl-CoA and provides NADPH for fatty acid synthesis, and, in subsequent pathways, generates NAD + for glycolysis. Citrate also activates acetyl-CoA carboxylase, an enzyme that is essential in the fatty acid synthesis pathway. [11]