Acetyl-CoA acetylation

Acetyl -CoA Acetyl -CoA Acetyl -CoA Acetyl -CoA Acetyl -CoA Acetyl -CoA... 

Acetyl-CoA Acetyl-CoA Acetyl-CoA Acetyl-CoA Acetyl-CoA Acetyl-CoA... 

Pymvate dehydrogenase is a mitochondrial enzyme, and fatty acid synthesis is a cytosohc pathway, but the mitochondrial membrane is impermeable to acetyl-CoA. Acetyl-CoA is made available in the cytosol from citrate synthesized in the mitochondrion, transported into the cytosol and cleaved in a reaction catalyzed by ATP-citrate lyase. 

FIGURE 9. Endogenous lipoprotein metabolism. In liver cells, cholesterol and triglycerides are packaged into VLDL particles and exported into blood where VLDL is converted to IDL. Intermediate-density lipoprotein can be either cleared by hepatic LDL receptors or further metabolized to LDL. LDL can be cleared by hepatic LDL receptors or can enter the arterial wall, contributing to atherosclerosis. Acetyl CoA, acetyl coenzyme A Apo, apolipoprotein C, cholesterol CE, cholesterol ester FA, fatty acid HL, hepatic lipase HMG CoA, 3-hydroxy-3-methyglutaryl coenzyme A IDL, intermediate-density lipoprotein LCAT, lecithin-cholesterol acyltransferase LDL, low-density lipoprotein LPL, lipoprotein lipase VLDL, very low-density lipoprotein. 

Figure 13.3. An overview of the chemical events at a cholinergic synapse and agents commonly used to alter cholinergic transmission acetyl CoA, acetyl coenzyme A Ch, choline. Nicotine and scopolamine bind to nicotinic and muscarinic receptors, respectively (nicotine is an agonist while scopolamine is an antagonist). Most anti-Alzheimer drugs inhibit the action of the enzyme cholinesterase.

Figure 6.1 Pathways involved in glucose oxidation by plant cells (a) glycolysis, (b) Krebs cycle, (c) mitochondrial cytochrome chain. Under anoxic conditions. Reactions 1, 2 and 3 of glycolysis are catalysed by lactate dehydrogenase, pyruvate decarboxylase and alcohol dehydrogenase, respectively. ATP and ADP, adenosine tri- and diphosphate NAD and NADHa, oxidized and reduced forms of nicotinamide adenine dinucleotide PGA, phosphoglyceraldehyde PEP, phosphoenolpyruvate Acetyl-CoA, acetyl coenzyme A FP, flavoprotein cyt, cytochrome e, electron. (Modified from Fitter and Hay, 2002). Reprinted with permission from Elsevier...

Figure 2.14 Iriter-relationship between intermediary. metabolism of glucose, phospholipids and acetylcholine synthesis. Acetyl CoA acetyl coenzyme A CAT-catechol-O-methyltransferase AChE acetylcholinesterase.

Fig. 1. Energy metabolism in the normal myocardium (ATP adenosine-5 -triphosphate, ADP adenosine-5 -diphosphate, P phosphate, PDH pyruvate dehydrogenase complex, acetyl-CoA acetyl-coenzyme A, NADH and NAD" nicotinamide adenine dinucleotide (reduced and oxidized), FADH2 and FAD flavin adenine dinucleotide (reduced and oxidized).

Additional information < >(< > not inhibitory AMP, ADP, ATP, GMP, GDP, GTP, cAMP, cGMP, acetyl-CoA, acetyl phosphate, glucose 6-phosphate, glucose 1-phosphate, fructose 1,6-diphosphate, t-histidine, o-histidine [14])... 

Acetylcholinesterase 609,634, 636 pseudosubstrate of 636 Acetyl-CoA (acetyl-coenzyme A) 506s, 508, 881... 

Acetyl-CoA. Acetyl-coenzyme A, a high-energy ester of acetic acid that is important both in the tricarboxylic acid cycle and in fatty acid biosynthesis. 

A specific transport protein, the carnitine-acylcarnitine translocase, moves the fatty acylcarnitine into the mitochondrial matrix while returning carnitine from the matrix to the cytoplasm. Once inside the mitochondria, another enzyme, carnitine palmitoyltransferase II (CPT II), located on the matrix side of the mitochondrial inner membrane, catalyzes the reconversion of fatty acylcarnitine to fatty acyl-CoA. Intramitochondrial fatty acyl-CoA then undergoes (3-oxidation to generate acetyl-CoA.Acetyl-CoA can enter the Kreb s cycle for complete oxidation or, in the liver, be used for the synthesis of acetoacetate and P-hydroxybutyrate (ketone bodies). 

Fats are catabolised by hydrolysis to free fatty acids and glycerol. Tbe free fatty acid is metabolised in the liver and peripheral tissue via /S-oxidation into acetyl CoA acetyl-CoA then enters the TCA cycle. Glycerol is used by the liver for triacylglycerol synthesis or for gluconeogenesis (following its conversion to 3-phosphoglycerate). 

Acetyl-CoA synthetase catalyses the conversion of acetic acid to acetyl-CoA ATP + Acetate + CoA - AMP - - Pyrophosphate + Acetyl-CoA Acetyl-CoA can enter the TCA cycle or be used in fatty acid synthesis. 

Quandt L and Huth W (1984) Modulation of rat-liver mitochondrial acetyl-CoA acetyl-transferase activity by a reversible chemical modification with coenzyme A. Biochim-ica et BiophysicaActa 784,168-76. 

The broad definition of lipids allows the inclusion of cholesterol, a molecule which contains many hydrocarbon groups and is not too soluble in water. Cholesterol contains a skeleton sterol ring (fig. 4.1), and is the precursor of other sterol-pontaining molecules, including the steroid hormones and bile acids (H-11). Cholesterol is ingested in the diet but may also be synthesized. All the carbons of cholesterol come from acetyl CoA. Acetyl CoA units... 

Fatty acid synthesis and degradation. Fatty acids are synthesized in the cytosol by the addition of two-carbon units to a growing chain on an acyl carrier protein. Malonyl CoA, the activated intermediate, is formed by the carboxylation of acetyl CoA. Acetyl groups are carried from mitochondria to the cytosol as citrate by the citrate-malate shuttle. In the cytosol, citrate is cleaved to yield acetyl CoA. In addition to transporting acetyl CoA, citrate in the cytosol stimulates acetyl CoA carboxylase, the enzyme catalyzing the committed step. When ATP and acetyl CoA are abundant, the level of citrate increases, which accelerates the rate of fatty acid synthesis (Figure 30.8). 

Acetate is synthesized via the acetyl-CoA pathway (for recent reviews see refs. [190-192]) one molecule CO2 is reduced via formyl-tetrahydrofolate (formyl-H4F) and methylene—H4F to methyl-H4F, a second one is reduced to a enzyme-bound carbonyl. The methyl group is condensed with the carbonyl group and coenzyme A (CoA) to acetyl-CoA. Acetyl-CoA is then converted to acetate, and ATP is formed in the acetate kinase reaction. 

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