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Showing 241 - 260 of 55724 compounds

Compound ID

Compound

Pathways

PW_C000514

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Copper

Copper is an essential nutrient to all higher plants and animals. Physiologically, it exists as an ion in the body. In animals, it is found primarily in the bloodstream, as a cofactor in various enzymes, and in copper-based pigments. In the body, copper shifts between the cuprous (Cu1+) and cupric (Cu2+) forms, though the majority of the body's copper is in the Cu2+ form. The ability of copper to easily accept and donate electrons explains its important role in oxidation-reduction (redox) reactions and in scavenging free radicals. Copper is a critical functional component of a number of essential enzymes known as cuproenzymes. For instance, the copper-dependent enzyme, cytochrome c oxidase, plays a critical role in cellular energy production. By catalyzing the reduction of molecular oxygen (O2) to water (H2O), cytochrome c oxidase generates an electrical gradient used by the mitochondria to create the vital energy-storing molecule, ATP. Another cuproenzyme, lysyl oxidase, is required for the cross-linking of collagen and elastin, which are essential for the formation of strong and flexible connective tissue. Another cuproeznyme, Monoamine oxidase (MAO), plays a role in the metabolism of the neurotransmitters norepinephrine, epinephrine, and dopamine. MAO also functions in the degradation of the neurotransmitter serotonin, which is the basis for the use of MAO inhibitors as antidepressants. One of the most important cuproenzymes is Superoxide dismutase (SOD). SOD functions as an antioxidant by catalyzing the conversion of superoxide radicals (free radicals or ROS) to hydrogen peroxide, which can subsequently be reduced to water by other antioxidant enzymes. Two forms of SOD contain copper: 1) copper/zinc SOD is found within most cells of the body, including red blood cells, and 2) extracellular SOD is a copper-containing enzyme found at high levels in the lungs and low levels in blood plasma. In sufficient amounts, copper can be poisonous or even fatal to organisms. Copper is normally bound to cuproenzymes (such as SOD, MOA) and is thus only toxic when unsequestered and unmediated. It is believed that zinc and copper compete for absorption in the digestive tract so that a diet that is excessive in one of these minerals may result in a deficiency in the other. An imbalance of zinc and copper status might be involved in human hypertension.

PW_C000517

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D-Fructose

Fructose, or levulose, is a levorotatory monosaccharide and an isomer of glucose (C6H12O6). The chemical composition of fructose is (C6H12O6). Pure fructose has a sweet taste similar to cane sugar, but with a "fruity" aroma. Although fructose is a hexose (6-carbon sugar), it generally exists as a 5-member hemiketal ring (a furanose). This structure is responsible for the long metabolic pathway and high reactivity compared to glucose. Fructose is found in many foods and is one of the three most important blood sugars along with glucose and galactose. Honey, tree fruits, berries, melons, and some root vegetables, such as beets, sweet potatoes, parsnips, and onions contain fructose, usually in combination with sucrose and glucose. Fructose is also derived from the digestion of sucrose, a disaccharide consisting of glucose and fructose that is broken down by enzymes during digestion. Fructose is the sweetest naturally occurring sugar, estimated to be twice as sweet as sucrose. It is used as a preservative and an intravenous infusion in parenteral feeding. Fructose is a reducing sugar, as are all monosaccharides. The spontaneous addition of single sugar molecules to proteins, known as glycation, is a significant cause of damage in diabetics. Fructose appears to be as dangerous as glucose in this regard, and therefore does not seem to be the answer for diabetes (McPherson et al, 1988). This may be an important contribution to senescence and many age-related chronic diseases (Levi & Werman 1998).

PW_C000530

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Linoleic acid

Linoleic acid is a doubly unsaturated fatty acid, also known as an omega-6 fatty acid, occurring widely in plant glycosides. In this particular polyunsaturated fatty acid (PUFA), the first double bond is located between the sixth and seventh carbon atom from the methyl end of the fatty acid (n-6). Linoleic acid is an essential fatty acid in human nutrition because it cannot be synthesized by humans. It is used in the biosynthesis of prostaglandins (via arachidonic acid) and cell membranes. (From Stedman, 26th ed).

PW_C000531

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PA(16:0/16:0)

PA(16:0/16:0)is a phosphatidic acid. It is a glycerophospholipid in which a phosphate moiety occupies a glycerol substitution site. As is the case with diacylglycerols, phosphatidic acids can have many different combinations of fatty acids of varying lengths and saturation attached at the C-1 and C-2 positions. Fatty acids containing 16, 18 and 20 carbons are the most common. PA(16:0/16:0), in particular, consists of two hexadecanoyl chain at positions C-1 and C2. The oleic acid moiety is derived from vegetable oils, especially olive and canola oil, while the oleic acid moiety is derived from vegetable oils, especially olive and canola oil. Phosphatidic acids are quite rare but are extremely important as intermediates in the biosynthesis of triacylglycerols and phospholipids.

PW_C000538

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L-Kynurenine

Kynurenine is a metabolite of the amino acid tryptophan used in the production of niacin. L-Kynurenine is a central compound of the tryptophan metabolism pathway since it can change into the neuroprotective agent kynurenic acid or to the neurotoxic agent quinolinic acid. The break-up of these endogenous compounds' balance can be observable in many disorders such as stroke, epilepsy, multiple sclerosis, and amyotrophic lateral sclerosis. It can also occur in neurodegenerative disorders such as Parkinson's disease, Huntington's, and Alzheimer's disease; and in mental disorders such as schizophrenia and depression.

PW_C000540

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L-Leucine

Branched chain amino acids (BCAA) are essential amino acids whose carbon structure is marked by a branch point. These three amino acids are critical to human life and are particularly involved in stress, energy and muscle metabolism. BCAA supplementation as therapy, both oral and intravenous, in human health and disease holds great promise. 'BCAA' denotes valine, isoleucine and leucine which are branched chain essential amino acids. Despite their structural similarities, the branched amino acids have different metabolic routes, with valine going solely to carbohydrates, leucine solely to fats and isoleucine to both. The different metabolism accounts for different requirements for these essential amino acids in humans: 12 mg/kg, 14 mg/kg and 16 mg/kg of valine, leucine and isoleucine respectively. Furthermore, these amino acids have different deficiency symptoms. Valine deficiency is marked by neurological defects in the brain, while isoleucine deficiency is marked by muscle tremors. Many types of inborn errors of BCAA metabolism exist, and are marked by various abnormalities. The most common form is the maple syrup urine disease, marked by a characteristic urinary odor. Other abnormalities are associated with a wide range of symptoms, such as mental retardation, ataxia, hypoglycemia, spinal muscle atrophy, rash, vomiting and excessive muscle movement. Most forms of BCAA metabolism errors are corrected by dietary restriction of BCAA and at least one form is correctable by supplementation with 10 mg of biotin daily. BCAA are useful because they are metabolized primarily by muscle. Stress state- e.g surgery, trauma, cirrhosis, infections, fever and starvation--require proportionately more BCAA than other amino acids and probably proportionately more leucine than either valine or isoleucine. BCAA and other amino acids are frequently fed intravenously (TPN) to malnourished surgical patients and in some cases of severe trauma. BCAA, particularly leucine, stimulate protein synthesis, increase reutilization of amino acids in many organs and reduce protein breakdown. Furthermore, leucine can be an important source of calories, and is superior as fuel to the ubiquitous intravenous glucose (dextrose). Leucine also stimulates insulin release, which in turn stimulates protein synthesis and inhibits protein breakdown. These effects are particularly useful in athletic training. BCAA should also replace the use of steroids as commonly used by weightlifters. Huntington's chorea and anorexic disorders both are characterized by low serum BCAA. These diseases, as well as forms of Parkinson's, may respond to BCAA therapy. BCAA, and particularly leucine, are among the amino acids most essential for muscle health. (http://www.dcnutrition.com).

PW_C000543

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Malonic acid

Malonic acid (IUPAC systematic name: propanedioic acid) is a dicarboxylic acid with structure CH2(COOH)2. The ionised form of malonic acid, as well as its esters and salts, are known as malonates. For example, diethyl malonate is malonic acid's ethyl ester. The name originates from Latin malum, meaning apple. Malonic acid is the archetypal example of a competitive inhibitor: it acts against succinate dehydrogenase (complex II) in the respiratory electron transport chain.

PW_C000544

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Fe2+

Iron is a chemical element with the symbol Fe and atomic number 26. Iron makes up 5% of the Earth's crust and is second in abundance to aluminium among the metals and fourth in abundance among the elements. Physiologically, it. exists as an ion in the body. Iron (as Fe2+, ferrous ion) is a necessary trace element used by all known living organisms. Iron-containing enzymes, usually containing heme prosthetic groups, participate in catalysis of oxidation reactions in biology, and in transport of a number of soluble gases. Iron is an essential constituent of hemoglobin, cytochrome, and other components of respiratory enzyme systems. Its chief functions are in the transport of oxygen to tissue (hemoglobin) and in cellular oxidation mechanisms. Inorganic iron involved in redox reactions is also found in the iron-sulfur clusters of many enzymes, such as nitrogenase (involved in the synthesis of ammonia from nitrogen and hydrogen) and hydrogenase. A class of non-heme iron proteins is responsible for a wide range of functions such as ribonucleotide reductase (reduces ribose to deoxyribose; DNA biosynthesis) and purple acid phosphatase (hydrolysis of phosphate esters). When the body is fighting a bacterial infection, the body sequesters iron inside of cells (mostly stored in the storage molecule ferritin) so that it cannot be used by bacteria. Depletion of iron stores may result in iron-deficiency anemia. Iron is used to build up the blood in anemia. Humans experience iron toxicity above 20 milligrams of iron for every kilogram of weight, and 60 milligrams per kilogram is a lethal dose. Over-consumption of iron, often the result of children eating large quantities of ferrous sulfate tablets intended for adult consumption, is the most common toxicological cause of death in children under six. The DRI lists the Tolerable Upper Intake Level (UL) for adults as 45 mg/day. For children under fourteen years old the UL is 40 mg/day. Iron is a metal extracted from iron ore, and is almost never found in the free elemental state.

PW_C000547

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Ketoleucine

Ketoleucine is an abnormal metabolite that arises from the incomplete breakdown of branched-chain amino acids. Ketoleucine is both a neurotoxin and a metabotoxin. A neurotoxin causes damage to nerve cells and nerve tissues. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of ketoleucine are associated with maple syrup urine disease (MSUD). MSUD is a metabolic disorder caused by a deficiency of the branched-chain alpha-keto acid dehydrogenase complex (BCKDC), leading to a buildup of the branched-chain amino acids (leucine, isoleucine, and valine) and their toxic by-products (ketoacids) in the blood and urine. The symptoms of MSUD often show in infancy and lead to severe brain damage if untreated. MSUD may also present later depending on the severity of the disease. If left untreated in older individuals, during times of metabolic crisis, symptoms of the condition include uncharacteristically inappropriate, extreme, or erratic behaviour and moods, hallucinations, anorexia, weight loss, anemia, diarrhea, vomiting, dehydration, lethargy, oscillating hypertonia and hypotonia, ataxia, seizures, hypoglycemia, ketoacidosis, opisthotonus, pancreatitis, rapid neurological decline, and coma. In maple syrup urine disease, the brain concentration of branched-chain ketoacids can increase 10- to 20-fold. This leads to a depletion of glutamate and a consequent reduction in the concentration of brain glutamine, aspartate, alanine, and other amino acids. The result is a compromise of energy metabolism because of a failure of the malate-aspartate shuttle and a diminished rate of protein synthesis (PMID: 15930465).

PW_C000548

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L-Methionine

Methionine is an essential amino acid (there are 9 essential amino acids) required for normal growth and development of humans, other mammals, and avian species. In addition to being a substrate for protein synthesis, it is an intermediate in transmethylation reactions, serving as the major methyl group donor in vivo, including the methyl groups for DNA and RNA intermediates. Methionine is a methyl acceptor for 5-methyltetrahydrofolate-homocysteine methyltransferase (methionine synthase), the only reaction that allows for the recycling of this form of folate, and is also a methyl acceptor for the catabolism of betaine. Methionine is the metabolic precursor for cysteine. Only the sulfur atom from methionine is transferred to cysteine; the carbon skeleton of cysteine is donated by serine (PMID: 16702340). There is a general consensus concerning normal sulfur amino acid (SAA) requirements. WHO recommendations amount to 13 mg/kg per 24 h in healthy adults. This amount is roughly doubled in artificial nutrition regimens. In disease or after trauma, requirements may be altered for methionine, cysteine, and taurine. Although in specific cases of congenital enzyme deficiency, prematurity, or diminished liver function, hypermethioninemia or hyperhomocysteinemia may occur, SAA supplementation can be considered safe in amounts exceeding 2-3 times the minimum recommended daily intake. Apart from some very specific indications (e.g. acetaminophen poisoning) the usefulness of SAA supplementation is not yet established (PMID: 16702341). Methionine is known to exacerbate psychopathological symptoms in schizophrenic patients, but there is no evidence of similar effects in healthy subjects. The role of methionine as a precursor of homocysteine is the most notable cause for concern. Acute doses of methionine can lead to acute increases in plasma homocysteine, which can be used as an index of the susceptibility to cardiovascular disease. Sufficiently high doses of methionine can actually result in death. Longer-term studies in adults have indicated no adverse consequences of moderate fluctuations in dietary methionine intake, but intakes higher than 5 times the normal amount resulted in elevated homocysteine levels. These effects of methionine on homocysteine and vascular function are moderated by supplements of vitamins B-6, B-12, C, and folic acid (PMID: 16702346). When present in sufficiently high levels, methionine can act as an atherogen and a metabotoxin. An atherogen is a compound that when present at chronically high levels causes atherosclerosis and cardiovascular disease. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of methionine are associated with at least ten inborn errors of metabolism, including cystathionine beta-synthase deficiency, glycine N-methyltransferase deficiency, homocystinuria, tyrosinemia, galactosemia, homocystinuria-megaloblastic anemia due to defects in cobalamin metabolism, methionine adenosyltransferase deficiency, methylenetetrahydrofolate reductase deficiency, and S-adenosylhomocysteine (SAH) hydrolase deficiency. Chronically elevated levels of methionine in infants can lead to intellectual disability and other neurological problems, delays in motor skills, sluggishness, muscle weakness, and liver problems. Many individuals with these metabolic disorders tend to develop cardiovascular disease later in life. Studies on feeding rodents high levels of methionine have shown that methionine promotes atherosclerotic plaques independently of homocysteine levels (PMID: 26647293). A similar study in Finnish men showed the same effect (PMID: 16487911).

PW_C000550

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Lithocholic acid glycine conjugate

Lithocholic acid glycine conjugate is an acyl glycine and a bile acid-glycine conjugate. is an acyl glycine and a bile acid-glycine conjugate. It is a secondary bile acid produced by the action of enzymes existing in the microbial flora of the colonic environment. In hepatocytes, both primary and secondary bile acids undergo amino acid conjugation at the C-24 carboxylic acid on the side chain, and almost all bile acids in the bile duct therefore exist in a glycine conjugated form (PMID:16949895). Bile acids are steroid acids found predominantly in bile of mammals. The distinction between different bile acids is minute, depends only on presence or absence of hydroxyl groups on positions 3, 7, and 12. Bile acids are physiological detergents that facilitate excretion, absorption, and transport of fats and sterols in the intestine and liver. Bile acids are also steroidal amphipathic molecules derived from the catabolism of cholesterol. They modulate bile flow and lipid secretion, are essential for the absorption of dietary fats and vitamins, and have been implicated in the regulation of all the key enzymes involved in cholesterol homeostasis. Bile acids recirculate through the liver, bile ducts, small intestine and portal vein to form an enterohepatic circuit. They exist as anions at physiological pH and, consequently, require a carrier for transport across the membranes of the enterohepatic tissues. The unique detergent properties of bile acids are essential for the digestion and intestinal absorption of hydrophobic nutrients. Bile acids have potent toxic properties (e.g., membrane disruption) and there are a plethora of mechanisms to limit their accumulation in blood and tissues. (PMID: 11316487, 16037564, 12576301, 11907135).

PW_C000551

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1-Methylnicotinamide

1-Methylnicotinamide is a metabolite of nicotinamide and is produced primarily in the liver. It has anti-inflammatory properties (PMID 16197374). It is a product of nicotinamide N-methyltransferase [EC 2.1.1.1] in the pathway of nicotinate and nicotinamide metabolism (KEGG). 1-Methylnicotinamide may be an endogenous activator of prostacyclin production and thus may regulate thrombotic as well as inflammatory processes in the cardiovascular system (PMID: 17641676).

PW_C000552

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Hydroxypropionic acid

3-Hydroxypropionic acid is a carboxylic acid. It is an intermediate in the breakdown of branched-chain amino acids and propionic acid from the gut. Typically it originates from propionyl-CoA and a defect in the enzyme propionyl carboxylase. This leads to a buildup in propionyl-CoA in the mitochondria. Such a buildup can lead to a disruption of the esterified CoA:free CoA ratio and ultimately to mitochondrial toxicity. Detoxification of these metabolic end products occurs via the transfer of the propionyl moiety to carnitine-forming propionyl-carnitine, which is then transferred across the inner mitochondrial membrane. 3-Hydroxypropionic acid is then released as the free acid. As an industrial chemical, it is used in the production of various chemicals such as acrylates in industry. When present in sufficiently high levels, 3-hydroxypropionic acid can act as an acidogen and a metabotoxin. An acidogen is an acidic compound that induces acidosis, which has multiple adverse effects on many organ systems. A metabotoxin is an endogenously produced metabolite that causes adverse health effects at chronically high levels. Chronically high levels of hydroxypropionic acid are associated with many inborn errors of metabolism including biotinidase deficiency, malonic aciduria, methylmalonate semialdehyde dehydrogenase deficiency, methylmalonic aciduria, methylmalonic aciduria due to cobalamin-related disorders, and propionic acidemia. Hydroxypropionic acid is an organic acid. Abnormally high levels of organic acids in the blood (organic acidemia), urine (organic aciduria), the brain, and other tissues lead to general metabolic acidosis. Acidosis typically occurs when arterial pH falls below 7.35. Infants with acidosis have symptoms that include poor feeding, vomiting, loss of appetite, weak muscle tone (hypotonia), and lack of energy (lethargy). These can progress to heart, liver, and kidney abnormalities, seizures, coma, and possibly death. These are also the characteristic symptoms of the IEMs mentioned above. Many affected children with organic acidemias experience intellectual disability or delayed development. In adults, acidosis or acidemia is characterized by headaches, confusion, feeling tired, tremors, sleepiness, and seizures.

PW_C000558

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4-Hydroxyphenylpyruvic acid

4-Hydroxyphenylpyruvic acid (4-HPPA) is a keto acid that is involved in the tyrosine catabolism pathway. It is a product of the enzyme (R)-4-hydroxyphenyllactate dehydrogenase [EC 1.1.1.222] and is formed during tyrosine metabolism. The conversion from tyrosine to 4-HPPA is catalyzed by tyrosine aminotransferase. Additionally, 4-HPPA can be converted to homogentisic acid which is one of the precursors to ochronotic pigment. The enzyme 4-hydroxyphenylpyruvic acid dioxygenase (HPD) catalyzes the reaction that converts 4-hydroxyphenylpyruvic acid to homogentisic acid. A deficiency in the catalytic activity of HPD is known to lead to tyrosinemia type III, an autosomal recessive disorder characterized by elevated levels of blood tyrosine and massive excretion of tyrosine derivatives into urine. It has been shown that hawkinsinuria, an autosomal dominant disorder characterized by the excretion of 'hawkinsin,' may also be a result of HPD deficiency (PMID: 11073718). There are two isomers of HPPA, specifically 4HPPA and 3HPPA, of which 4HPPA is the most common.

PW_C000566

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Kynurenic acid

Kynurenic acid (KYNA) is a well-known endogenous antagonist of the glutamate ionotropic excitatory amino acid receptors N-methyl-D-aspartate (NMDA), alphaamino-3-hydroxy-5-methylisoxazole-4-propionic acid and kainate receptors and of the nicotine cholinergic subtype alpha 7 receptors. KYNA neuroprotective and anticonvulsive activities have been demonstrated in animal models of neurodegenerative diseases. Because of KYNA's neuromodulatory character, its involvement has been speculatively linked to the pathogenesis of a number of neurological conditions including those in the ageing process. Different patterns of abnormalities in various stages of KYNA metabolism in the CNS have been reported in Alzheimer's disease, Parkinson's disease and Huntington's disease. In HIV-1-infected patients and in patients with Lyme neuroborreliosis a marked rise of KYNA metabolism was seen. In the ageing process KYNA metabolism in the CNS of rats shows a characteristic pattern of changes throughout the life span. A marked increase of the KYNA content in the CNS occurs before the birth, followed by a dramatic decline on the day of birth. A low activity was seen during ontogenesis, and a slow and progressive enhancement occurs during maturation and ageing. This remarkable profile of KYNA metabolism alterations in the mammalian brain has been suggested to result from the development of the organisation of neuronal connections and synaptic plasticity, development of receptor recognition sites, maturation and ageing. There is significant evidence that KYNA can improve cognition and memory, but it has also been demonstrated that it interferes with working memory. Impairment of cognitive function in various neurodegenerative disorders is accompanied by profound reduction and/or elevation of KYNA metabolism. The view that enhancement of CNS KYNA levels could underlie cognitive decline is supported by the increased KYNA metabolism in Alzheimer's disease, by the increased KYNA metabolism in down's syndrome and the enhancement of KYNA function during the early stage of Huntington's disease. Kynurenic acid is the only endogenous N-methyl-D-aspartate (NMDA) receptor antagonist identified up to now, that mediates glutamatergic hypofunction. Schizophrenia is a disorder of dopaminergic neurotransmission, but modulation of the dopaminergic system by glutamatergic neurotransmission seems to play a key role. Despite the NMDA receptor antagonism, kynurenic acid also blocks, in lower doses, the nicotinergic acetycholine receptor, i.e., increased kynurenic acid levels can explain psychotic symptoms and cognitive deterioration. Kynurenic acid levels are described to be higher in the cerebrospinal fluid (CSF) and in critical central nervous system (CNS) regions of schizophrenics as compared to controls. (PMID: 17062375, 16088227).

PW_C000567

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L-Pipecolic acid

L-Pipecolic acid is a normal human metabolite present in human blood, where is present as the primary enantiomer of pipecolic acid. L-Pipecolic acid is a cyclic imino acid produced during the degradation of lysine, accumulates in body fluids of infants with generalized genetic peroxisomal disorders, including Zellweger syndrome (OMIM 214100), neonatal adrenoleukodystrophy (OMIM 202370), and infantile Refsum disease (OMIM 266510). L-Pipecolic acid levels are also elevated in patients with chronic liver diseases. L-Pipecolic acid is the substrate of delta1-piperideine-2-carboxylate reductase [EC 1.5.1.21] in the pathway of lysine degradation. (PMID: 2717271, 8305590, 1050990).

PW_C000570

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L-Homoserine

Homoserine is a more reactive variant of the amino acid serine. In this variant, the hydroxyl side chain contains an additional CH2 group which brings the hydroxyl group closer to its own carboxyl group, allowing it to chemically react to form a five-membered ring. This occurs at the point that amino acids normally join to their neighbours in a peptide bond. Homoserine is therefore unsuitable for forming proteins and has been eliminated from the repertoire of amino acids used by living things. Homoserine is the final product on the C-terminal end of the N-terminal fragment following a cyanogen bromide cleavage. (wikipedia).

PW_C000573

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Lithocholyltaurine

Lithocholyltaurine is a bile salt formed in the liver from lithocholic acid conjugation with taurine, usually as the sodium salt. It solubilizes fats for absorption and is itself absorbed. Lithocholic acid, a hydrophobic secondary bile acid, is well known to cause intrahepatic cholestasis. There have been extensive studies on the mechanisms of lithocholate-induced cholestasis in animals. Lithocholate diminishes both the bile acid-dependent and independent bile flow. In humans, elevated levels of lithocholic acid are found in patients with chronic cholestatic liver disease. Lithocholyltaurine impairs both the bile canalicular contractions and the canalicular bile secretion, possibly by acting directly on the canalicular membranes in lithocholyltaurine-induced cholestasis. Lithocholyltaurine induce acute cholestasis-associated with retrieval of the bile salt export pump. The bile salt export pump (BSEP) of hepatocyte secretes conjugated bile salts across the canalicular membrane in an ATP-dependent manner. Hepatic retention of bile acids may lead to liver injury by hepatocyte apoptosis and eventually deterioration of cholestatic liver diseases. One mechanism of induced apoptosis by lithocholyltaurine is the induction of transcriptional activity of AP-1 (activation protein-1). (PMID: 16981261, 15763547, 16332456, 18164257).

PW_C000590

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Homocysteine

Homocysteine is a sulfur-containing amino acid that arises during methionine metabolism. Although its concentration in plasma is only about 10 micromolar (uM), even moderate hyperhomocysteinemia is associated with increased incidence of cardiovascular disease and Alzheimer's disease. Elevations in plasma homocysteine are commonly found as a result of vitamin deficiencies, polymorphisms of enzymes of methionine metabolism, and renal disease. Pyridoxal, folic acid, riboflavin, and Vitamin B(12) are all required for methionine metabolism, and deficiency of each of these vitamins result in elevated plasma homocysteine. A polymorphism of methylenetetrahydrofolate reductase (C677T), which is quite common in most populations with a homozygosity rate of 10-15 %, is associated with moderate hyperhomocysteinemia, especially in the context of marginal folate intake. Plasma homocysteine is inversely related to plasma creatinine in patients with renal disease. This is due to an impairment in homocysteine removal in renal disease. The role of these factors, and of modifiable lifestyle factors, in affecting methionine metabolism and in determining plasma homocysteine levels is discussed. Homocysteine is an independent cardiovascular disease (CVD) risk factor modifiable by nutrition and possibly exercise. Homocysteine was first identified as an important biological compound in 1932 and linked with human disease in 1962 when elevated urinary homocysteine levels were found in children with mental retardation. This condition, called homocysteinuria, was later associated with premature occlusive CVD, even in children. These observations led to research investigating the relationship of elevated homocysteine levels and CVD in a wide variety of populations including middle age and elderly men and women with and without traditional risk factors for CVD. (PMID 17136938, 15630149).

PW_C000592

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Malic acid

Malic acid is a tart-tasting organic dicarboxylic acid that plays a role in many sour or tart foods. In its ionised form it is malate, an intermediate of the TCA cycle along with fumarate. It can also be formed from pyruvate as one of the anaplerotic reactions.
Showing 241 - 260 of 55724 compounds