Ketogenesis
Ketogenesis is the biochemical process through which organisms produce ketone bodies by breaking down fatty acids and ketogenic amino acids. The process supplies energy to certain organs, particularly the brain, heart and skeletal muscle, under specific scenarios including fasting, caloric restriction, sleep, or others. (In rare metabolic diseases, insufficient gluconeogenesis can cause excessive ketogenesis and hypoglycemia, which may lead to the life-threatening condition known as non-diabetic ketoacidosis.) Ketone bodies are not obligately produced from fatty acids; rather a meaningful amount of them is synthesized only in a situation of carbohydrate and protein insufficiency, where only fatty acids are readily available as fuel for their production. Recent evidence suggests that glial cells are ketogenic, supplying neurons with locally synthesized ketone bodies to sustain cognitive processes. Production Ketone bodies are produced mainly in the mitochondria of liver cell ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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HMG-CoA
β-Hydroxy β-methylglutaryl-CoA (HMG-CoA), also known as 3-hydroxy-3-methylglutaryl coenzyme A, is an intermediate in the mevalonate pathway, mevalonate and ketogenesis pathways. It is formed from acetyl CoA and acetoacetyl CoA by HMG-CoA synthase. The research of Minor J. Coon and Bimal Kumar Bachhawat in the 1950s at University of Illinois led to its discovery. HMG-CoA is a metabolic intermediate in the metabolism of the branched-chain amino acids, which include leucine, isoleucine, and valine. Its immediate precursors are β-methylglutaconyl-CoA (MG-CoA) and β-hydroxy β-methylbutyryl-CoA (HMB-CoA). HMG-CoA reductase catalyzes the conversion of HMG-CoA to mevalonic acid, a necessary step in the biosynthesis of cholesterol. Biosynthesis Mevalonate pathway Mevalonate synthesis begins with the beta-ketothiolase-catalyzed Claisen condensation of two molecules of acetyl-CoA to produce Acetoacetyl-CoA, acetoacetyl CoA. The following reaction involves the joining of acetyl-C ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Ketone Bodies
Ketone bodies are water-soluble molecules or compounds that contain the ketone groups produced from fatty acids by the liver ( ketogenesis). 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.Silva, B., Mantha, O. L., Schor, J., Pascual, A., Plaçais, P. Y., Pavlowsky, A., & Preat, T. (2022). Glia fuel neurons with locally synthesized ketone bodies to sustain memory under starvation. Nature Metabolism, 4(2), 213–224. https://doi.org/10.1038/s42255-022-00528-6 These liver-derived ketone groups include acetoacetic acid (acetoacetate), beta-hydroxybutyrate, and acetone, a spontaneous breakdown product of acetoacetate (see graphic). Ketone bodies are produced by the liver during periods of caloric restriction of various scenarios: low food intake (fasting), carbohydrate restrictive diets, starvation, prolonged intense e ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Ketogenic Amino Acid
A ketogenic amino acid is an amino acid that can be degraded directly into acetyl-CoA, which is the precursor of ketone bodies and myelin, particularly during early childhood, when the developing brain requires high rates of myelin synthesis. This is in contrast to the glucogenic amino acids, which are converted into glucose. Ketogenic amino acids are unable to be converted to glucose as both carbon atoms in the ketone body are ultimately degraded to carbon dioxide in the citric acid cycle. In humans, two amino acids – leucine and lysine – are exclusively ketogenic. Five more are amphibolic (both ketogenic and glucogenic): phenylalanine, isoleucine, threonine, tryptophan and tyrosine. The remaining thirteen are exclusively glucogenic. Studies Ketogenic amino acids serve important roles in the human body, leading to the study of ketogenic amino acid rich (KAAR) diets as possible treatment for non-alcoholic fatty liver disease (NAFLD) and diabetes. Dietary studies of fatty liv ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Acetyl-CoA Carboxylase
Acetyl-CoA carboxylase (ACC) is a biotin-dependent enzyme () that catalyzes the irreversible carboxylation of acetyl-CoA to produce malonyl-CoA through its two catalytic activities, biotin carboxylase (BC) and carboxyltransferase (CT). ACC is a multi-subunit enzyme in most prokaryotes and in the chloroplasts of most plants and algae, whereas it is a large, multi-domain enzyme in the cytoplasm of most eukaryotes. The most important function of ACC is to provide the malonyl-CoA substrate for the biosynthesis of fatty acids. The activity of ACC can be controlled at the transcriptional level as well as by small molecule modulators and covalent modification. The human genome contains the genes for two different ACCs—'' ACACA'' and '' ACACB''. Structure Prokaryotes and plants have multi-subunit ACCs composed of several polypeptides. Biotin carboxylase (BC) activity, biotin carboxyl carrier protein (BCCP), and carboxyl transferase (CT) activity are each contained on a differ ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Oxaloacetate
Oxaloacetic acid (also known as oxalacetic acid or OAA) is a crystalline organic compound with the chemical formula HO2CC(O)CH2CO2H. Oxaloacetic acid, in the form of its conjugate base oxaloacetate, is a metabolic intermediate in many processes that occur in animals. It takes part in gluconeogenesis, the urea cycle, the glyoxylate cycle, amino acid synthesis, fatty acid synthesis and the citric acid cycle. Properties Oxaloacetic acid undergoes successive deprotonations to give the dianion: :HO2CC(O)CH2CO2H −O2CC(O)CH2CO2H + H+, pKa = 2.22 :−O2CC(O)CH2CO2H −O2CC(O)CH2CO2− + H+, pKa = 3.89 At high pH, the enolizable proton is ionized: :−O2CC(O)CH2CO2− −O2CC(O−)CHCO2− + H+, pKa = 13.03 The enol forms of oxaloacetic acid are particularly stable. Keto-enol tautomerization is catalyzed by the enzyme oxaloacetate tautomerase. ''trans''-Enol-oxaloacetate also appears when tartrate is the substrate for fumarase. Biosynthesis Oxaloacetate forms ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Electron Transport Chain
An electron transport chain (ETC) is a series of protein complexes and other molecules which transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples this electron transfer with the transfer of protons (H+ ions) across a membrane. Many of the enzymes in the electron transport chain are embedded within the membrane. The flow of electrons through the electron transport chain is an exergonic process. The energy from the redox reactions creates an electrochemical proton gradient that drives the synthesis of adenosine triphosphate (ATP). In aerobic respiration, the flow of electrons terminates with molecular oxygen as the final electron acceptor. In anaerobic respiration, other electron acceptors are used, such as sulfate. In an electron transport chain, the redox reactions are driven by the difference in the Gibbs free energy of reactants and products. The free energy released when ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Citric Acid Cycle
The citric acid cycle—also known as the Krebs cycle, Szent–Györgyi–Krebs cycle, or TCA cycle (tricarboxylic acid cycle)—is a series of chemical reaction, biochemical reactions that release the energy stored in nutrients through acetyl-CoA Redox, oxidation. The energy released is available in the form of Adenosine triphosphate, ATP. The Hans Krebs (biochemist), Krebs cycle is used by organisms that generate energy via Cellular respiration, respiration, either anaerobic respiration, anaerobically or aerobic respiration, aerobically (organisms that Fermentation, ferment use different pathways). In addition, the cycle provides precursor (chemistry), precursors of certain amino acids, as well as the reducing agent nicotinamide adenine dinucleotide, NADH, which are used in other reactions. Its central importance to many Metabolic pathway, biochemical pathways suggests that it was one of the earliest metabolism components. Even though it is branded as a "cycle", it is not necessa ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Acetyl-CoA
Acetyl-CoA (acetyl coenzyme A) is a molecule that participates in many biochemical reactions in protein, carbohydrate and lipid metabolism. Its main function is to deliver the acetyl group to the citric acid cycle (Krebs cycle) to be oxidation, oxidized for energy production. Coenzyme A (CoASH or CoA) consists of a cysteamine, β-mercaptoethylamine group linked to pantothenic acid (vitamin B5) through an amide linkage and 3'-phosphorylated ADP. The acetyl group (indicated in blue in the structural diagram on the right) of acetyl-CoA is linked to the sulfhydryl substituent of the β-mercaptoethylamine group. This thioester linkage is a "high energy" bond, which is particularly reactive. Hydrolysis of the thioester bond is exergonic (−31.5 kJ/mol). CoA is acetylated to acetyl-CoA by the breakdown of carbohydrates through glycolysis and by the breakdown of fatty acids through Beta oxidation, β-oxidation. Acetyl-CoA then enters the citric acid cycle, where the acetyl group is ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Beta Oxidation
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 FADH2, which are electron carriers used in the electron transport chain. It is named as such because the beta carbon of the fatty acid chain undergoes oxidation and is converted to a carbonyl group to start the cycle all over again. Beta-oxidation is primarily facilitated by the mitochondrial trifunctional protein, an enzyme complex associated with the inner mitochondrial membrane, although very long chain fatty acids are oxidized in peroxisomes. The overall reaction for one cycle of beta oxidation is: :C''n''-acyl-CoA + FAD + NAD''+'' + H''2''O + CoA → C''n''-2-acyl-CoA + FADH''2'' + NADH + H''+'' + acetyl-CoA Activation and membrane transport Free fatty acids cannot penetrate any bi ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Fatty Acid
In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated and unsaturated compounds#Organic chemistry, saturated or unsaturated. Most naturally occurring fatty acids have an Branched chain fatty acids, unbranched chain of an even number of carbon atoms, from 4 to 28. Fatty acids are a major component of the lipids (up to 70% by weight) in some species such as microalgae but in some other organisms are not found in their standalone form, but instead exist as three main classes of esters: triglycerides, phospholipids, and cholesteryl esters. In any of these forms, fatty acids are both important diet (nutrition), dietary sources of fuel for animals and important structural components for cell (biology), cells. History The concept of fatty acid (''acide gras'') was introduced in 1813 by Michel Eugène Chevreul, though he initially used some variant terms: ''graisse acide'' and ''acide huileux'' ("acid fat" and "oi ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |
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Diabetes Mellitus
Diabetes mellitus, commonly known as diabetes, is a group of common endocrine diseases characterized by sustained hyperglycemia, high blood sugar levels. Diabetes is due to either the pancreas not producing enough of the hormone insulin, or the cells of the body becoming unresponsive to insulin's effects. Classic symptoms include polydipsia (excessive thirst), polyuria (excessive urination), polyphagia (excessive hunger), Weight loss#Unintentional, weight loss, and blurred vision. If left untreated, the disease can lead to various health complications, including disorders of the Cardiovascular disease, cardiovascular system, Diabetic retinopathy, eye, Diabetic nephropathy, kidney, and Diabetic neuropathy, nerves. Diabetes accounts for approximately 4.2 million deaths every year, with an estimated 1.5 million caused by either untreated or poorly treated diabetes. The major types of diabetes are Type 1 diabetes, type 1 and Type 2 diabetes, type 2. The most common treatment for ty ... [...More Info...]       [...Related Items...]     OR:     [Wikipedia]   [Google]   [Baidu]   |