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Showing 181 - 200 of 55724 compounds

Compound ID




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Uric acid

Uric acid is a heterocyclic purine derivative that is the final oxidation product of purine metabolism. It is produced by the enzyme xanthine oxidase, which oxidizes oxypurines such as xanthine into uric acid. In most mammals, except humans and higher primates, the enzyme uricase further oxidizes uric acid to allantoin. Uric acid is also the end product of nitrogen metabolism in birds and reptiles. In such species, it is excreted in feces as a dry mass. Humans produce only small quantities of uric acid with excess accumulation leading to a type of arthritis known as gout. The loss of uricase in higher primates parallels the similar loss of the ability to synthesize ascorbic acid vitamin C. This may be because in higher primates uric acid partially replaces ascorbic acid.


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Uridine diphosphate-N-acetylglucosamine

Uridine diphosphate-N-acetylglucosamine (uridine 5'-diphosphate-GlcNAc, or UDP-Glc-NAc) is an acetylated aminosugar nucleotide. UDP-GlcNAc is the donor substrate for modification of nucleocytoplasmic proteins at serine and threonine residues with N-acetylglucosamine (O-GlcNAc). Nutrient sensing in mammals is done through the hexosamine biosynthetic pathway (HSP), which produces uridine 5'-diphospho-N-acetylglucosamine (UDP-Glc-NAc) as its end product. Mammals respond to nutrient excess by activating O-GlcNAcylation (addition of O-linked N-acetylglucosamine). O-GlcNAc addition (and removal) is key to histone remodeling, transcription, proliferation, apoptosis, and proteasomal degradation. This nutrient-responsive signaling pathway also modulates important cellular pathways, including the insulin signaling cascade in. Alterations in O-GlcNAc metabolism are associated with various human diseases including diabetes mellitus and neurodegeneration. (PMID: 16317114) Due to the chemical makeup of UDP-GlcNAc, it is well positioned to serve as a glucose sensor in that it is a high-energy compound that requires and/or responds to glucose, amino acid, fatty acid and nucleotide metabolism for synthesis. Elevated levels of O-GlcNAc have an effect on insulin-stimulated glucose uptake. (PMID: 12678487).


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Vanillylmandelic acid

Vanillylmandelic acid is one of the products of the catabolism of catecholamines (epinephrine, norepinephrine and dopamine). High levels of vanillylmandelic acid can indicate an adrenal gland tumor (pheochromocytoma) or another type of tumor that produces catecholamines. (WebMD).


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Xanthine is a purine base found in most body tissues and fluids, certain plants, and some urinary calculi. It is an intermediate in the degradation of adenosine monophosphate to uric acid, being formed by oxidation of hypoxanthine. The methylated xanthine compounds caffeine, theobromine, and theophylline and their derivatives are used in medicine for their bronchodilator effects. (Dorland, 28th ed.).


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Urea is a highly soluble organic compound formed in the liver from ammonia produced by the deamination of amino acids. It is the principal end product of protein catabolism and constitutes about one half of the total urinary solids. Urea is formed in a cyclic pathway known simply as the urea cycle. In this cycle, amino groups donated by ammonia and L-aspartate are converted to urea. Urea is essentially a waste product; it has no physiological function. It is dissolved in blood (in humans in a concentration of 2.5 - 7.5 mmol/liter) and excreted by the kidney in the urine. In addition, a small amount of urea is excreted (along with sodium chloride and water) in human sweat.


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Uridine 5'-diphosphate

Uridine 5'-diphosphate is a uracil nucleotide containing a pyrophosphate group esterified to C5 of the sugar moiety. UDP is an important extracellular pyrimidine signaling molecule that mediates diverse biological effects via P1 and P2 purinergic receptors, such as the uptake of thymidine and proliferation of gliomas. (PMID: 14558596). UDP induces intracellular Ca(2+) responses and oscillations in HeLa cells, due to the activation of P2Ys (G-protein coupled ATP receptors). (PMID: 1257952).


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Uridine, also known as beta-uridine or 1-beta-D-ribofuranosylpyrimidine-2,4(1H,3H)-dione, is a member of the class of compounds known as pyrimidine nucleosides. Pyrimidine nucleosides are compounds comprising a pyrimidine base attached to a ribosyl or deoxyribosyl moiety. More specifically, uridine is a nucleoside consisting of uracil and D-ribose and a component of RNA. Uridine is soluble (in water) and a very weakly acidic compound (based on its pKa). Uridine can be synthesized from uracil. It is one of the five standard nucleosides which make up nucleic acids; the others being adenosine, thymidine, cytidine, and guanosine. The five nucleosides are commonly abbreviated to their one-letter codes U, A, T, C, and G respectively. Uridine is also a parent compound for other transformation products, including but not limited to, nikkomycin Z, 3'-(enolpyruvyl)uridine 5'-monophosphate and 5-aminomethyl-2-thiouridine. Uridine can be found in most biofluids, including urine, breast milk, cerebrospinal fluid (CSF), and blood. Within the cell, uridine is primarily located in the mitochondria, in the nucleus, and in the lysosome. It can also be found in the extracellular space. As an essential nucleoside, uridine exists in all living species, ranging from bacteria to humans. In humans, uridine is involved in several metabolic disorders, some of which include dhydropyrimidinase deficiency, MNGIE (mitochondrial neurogastrointestinal encephalopathy), and beta-ureidopropionase deficiency. Uridine is a nucleoside consisting of uracil and D-ribose and is a component of RNA. Uridine plays a role in the glycolysis pathway of galactose. In humans there is no catabolic process to metabolize galactose. Therefore, galactose is converted to glucose and metabolized via the normal glucose metabolism pathways. More specifically, consumed galactose is converted into galactose 1-phosphate (Gal-1-P). This molecule is a substrate for the enzyme galactose-1-phosphate uridyl transferase which transfers a UDP molecule to the galactose molecule. The end result is UDP-galactose and glucose-1-phosphate. This process is continued to allow the proper glycolysis of galactose. Uridine is found in many foods (anything containing RNA) but is destroyed in the liver and gastrointestinal tract, and so no food, when consumed, has ever been reliably shown to elevate blood uridine levels. On the other hand, consumption of RNA-rich foods may lead to high levels of purines (adenine and guanosine) in blood. High levels of purines are known to increase uric acid production and may aggravate or lead to conditions such as gout.


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Biological Source: Xanthosine is produced by guanine-free mutants of bacteria e.g. Bacillus subtilis, Aerobacter aerogenes. Also reported from seeds of Trifolium alexandrinum Physical Description: Prismatic cryst. (H2O) (Chemnetbase) The deamination product of guanosine. Xanthosine monophosphate is an intermediate in purine metabolism, formed from IMP, and forming GMP.(Wikipedia). Xanthylic acid can be used in quantitative measurements of the Inosine monophosphate dehydrogenase enzyme activities in purine metabolism, as recommended to ensure optimal thiopurine therapy for children with acute lymphoblastic leukaemia (ALL). (PMID: 16725387).


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Uracil is a common naturally occurring pyrimidine found in RNA, it base pairs with adenine and is replaced by thymine in DNA. Methylation of uracil produces thymine. Uracil's use in the body is to help carry out the synthesis of many enzymes necessary for cell function through bonding with riboses and phosphates. Uracil serves as allosteric regulator and coenzyme for many important biochemical reactions. UDP and UTP regulate CPSase II activity in animals. UDP-glucose regulates the conversion of glucose to galactose in the liver and other tissues in the process of carbohydrate metabolism. Uracil is also involved in the biosynthesis of polysaccharides and the transportation of sugars containing aldehydes.


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Urocanic acid

Urocanic acid is a breakdown (deamination) product of histidine. In the liver, urocanic acid is an intermediate in the conversion of histidine to glutamic acid, whereas in the epidermis, it accumulates and may be both a UV protectant and an immunoregulator. Urocanic acid (UA) exists as a trans isomer (t-UA, approximately 30 mg/cm2) in the uppermost layer of the skin (stratum corneum). t-UA is formed as the cells of the second layer of skin become metabolically inactive. During this process, proteins and membranes degrade, histidine is released, and histidase (histidine ammonia lyase) catalyzes the deamination of histidine to form t-UA. t-UA accumulates in the epidermis until removal by either the monthly skin renewal cycle or sweat. Upon absorption of UV light, the naturally occurring t-UA isomerizes to its cis form, c-UA. Because DNA lesions (e.g., pyrimidine dimers) in the lower epidermis can result from UV-B absorption, initial research proposed that t-UA acted as a natural sunscreen absorbing UV-B in the stratum corneum before the damaging rays could penetrate into lower epidermal zones. Researchers have found that c-UA also suppresses contact hypersensitivity and delayed hypersensitivity, reduces the Langerhans cell count in the epidermis, prolongs skin-graft survival time, and affects natural killer cell activity.


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Uridine diphosphategalactose

Uridine diphosphategalactose (UDPgal) is a nucleoside diphosphate sugar which can be epimerized into UDPglucose for entry into the mainstream of carbohydrate metabolism. UDPgal is a pivotal compound in the metabolism of galactose. UDPgal is a product of the galactose-l-phosphate uridyl transferase (EC reaction but may also be made from Glucose-l-P, involving uridine diphosphate galactose-4-epimerase (EC UDPgal is the necessary galactosyl donor of galactose in the metabolism to incorporate it into complex oligosaccharides, glycoproteins and glycolipids (galactosides). Defective galactosylation of complex glycoconjugates exists in tissues from galactosemic patients. There is a tendency for galactosemic red cell UDPgal to be in the low normal range with a high uridine diphosphate glucose to UDP-gal ratio. This may reflect an inability of red cell UDPgal-4'-epimerase to maintain a normal ratio and consequently higher levels of UDPgal. In the more complex white blood cells and cultured fibroblasts, the UDPgal content and the uridine diphosphate glucose to UDPgal ratio of galactosemics are normal. Therefore, defective galactosylation observed in galactosemic fibroblasts must result from a defect in the transfer of galactose from UDPgal to these moieties. (PMID: 2122114, 7671968).


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Tryptamine is a monoamine compound that is common precursor molecule to many hormones and neurotransmitters. Biosynthesis generally proceeds from the amino acid tryptophan, with tryptamine in turn acting as a precursor for other compounds. Substitutions to the tryptamine molecule give rise to a group of compounds collectively known as tryptamines. The most well-known tryptamines are serotonin, an important neurotransmitter, and melatonin, a hormone involved in regulating the sleep-wake cycle.


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Vitamin A

Vitamin A (retinol) is a yellow fat-soluble, antioxidant vitamin important in vision and bone growth. It belongs to the family of chemical compounds known as retinoids. Retinol is ingested in a precursor form; animal sources (milk and eggs) contain retinyl esters, whereas plants (carrots, spinach) contain pro-vitamin A carotenoids. Hydrolysis of retinyl esters results in retinol while pro-vitamin A carotenoids can be cleaved to produce retinal. Retinal, also known as retinaldehyde, can be reversibly reduced to produce retinol or it can be irreversibly oxidized to produce retinoic acid. Retinol and derivatives of retinol that play an essential role in metabolic functioning of the retina, the growth of and differentiation of epithelial tissue, the growth of bone, reproduction, and the immune response. Dietary vitamin A is derived from a variety of carotenoids found in plants. It is enriched in the liver, egg yolks, and the fat component of dairy products.


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Tyramine is a monoamine compound derived from the amino acid tyrosine. Tyramine is metabolized by the enzyme monoamine oxidase. In foods, it is often produced by the decarboxylation of tyrosine during fermentation or decay. Foods containing considerable amounts of tyramine include fish, chocolate, alcoholic beverages, cheese, soy sauce, sauerkraut, and processed meat. A large dietary intake of tyramine can cause an increase in systolic blood pressure of 30 mmHg or more. Tyramine acts as a neurotransmitter via a G protein-coupled receptor with high affinity for tyramine called TA1. The TA1 receptor is found in the brain as well as peripheral tissues including the kidney. An indirect sympathomimetic, Tyramine can also serve as a substrate for adrenergic uptake systems and monoamine oxidase so it prolongs the actions of adrenergic transmitters. It also provokes transmitter release from adrenergic terminals.


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3,4-Dihydroxyphenylglycol (DOPEG) is a normal norepinephrine metabolite present in CSF, plasma and urine in humans (PMID 6875564). In healthy individuals there is a tendency for free DOPEG to increase and for conjugated DOPEG to decrease with age; plasmatic DOPEG levels are significantly lower in depressed patients as compared to healthy controls (PMID 6671452).


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18-Hydroxycorticosterone is a corticosteroid and a derivative of corticosterone. If it is present in sufficiently high concentrations, it can lead to serious electrolyte imbalances (an electrolyte toxin). 18-Hydroxycorticosterone serves as an intermediate in the synthesis of aldosterone by the enzyme aldosterone synthase in the zona glomerulosa. Chronically high levels of 18-hydroxycorticosterone are associated with at least three inborn errors of metabolism including adrenal hyperplasia type V, corticosterone methyl oxidase I deficiency, and corticosterone methyl oxidase II deficiency. Each of these conditions is characterized by excessive amounts of sodium being released in the urine (salt wasting), along with insufficient release of potassium in the urine, usually beginning in the first few weeks of life. This imbalance leads to low levels of sodium and high levels of potassium in the blood (hyponatremia and hyperkalemia, respectively). Individuals with corticosterone methyloxidase deficiency can also have high levels of acid in the blood (metabolic acidosis). Acidosis typically occurs when arterial pH falls below 7.35. In infants with acidosis the initial symptoms include poor feeding, vomiting, loss of appetite, weak muscle tone (hypotonia), and lack of energy (lethargy). The hyponatremia, hyperkalemia, and metabolic acidosis associated with corticosterone methyloxidase deficiency can cause nausea, vomiting, dehydration, low blood pressure, extreme tiredness (fatigue), and muscle weakness.


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Estrone (also oestrone) is an estrogenic hormone secreted by the ovary. Its molecular formula is C18H22O2. estrone has a melting point of 254.5 degrees Celsius. estrone is one of the three estrogens, which also include estriol and estradiol. estrone is the least prevalent of the three hormones, estradiol being prevalent almost always in a female body, estriol being prevalent primarily during pregnancy. estrone sulfate is relevant to health and disease due to its conversion to estrone sulfate, a long-lived derivative of estrone. estrone sulfate acts as a pool of estrone which can be converted as needed to the more active estradiol.


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Estrone (also oestrone) is an estrogenic hormone secreted by the ovary. Its molecular formula is C18H22O2. estrone has a melting point of 254.5 degrees Celsius. estrone is one of the three estrogens, which also include estriol and estradiol. estrone is the least prevalent of the three hormones, estradiol being prevalent almost always in a female body, estriol being prevalent primarily during pregnancy. estrone sulfate is relevant to health and disease due to its conversion to estrone sulfate, a long-lived derivative of estrone. estrone sulfate acts as a pool of estrone which can be converted as needed to the more active estradiol.


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3-Hydroxybutyric acid

3-Hydroxybutyric acid (or beta-hydroxybutyrate) is a ketone body. Like the other ketone bodies (acetoacetate and acetone), levels of 3-hydroxybutyrate in blood and urine are raised in ketosis. In humans, 3-hydroxybutyrate is synthesized in the liver from acetyl-CoA and can be used as an energy source by the brain when blood glucose is low. Blood levels of 3-hydroxybutyric acid levels may be monitored in diabetic patients to look for diabetic ketoacidosis. Persistent mild hyperketonemia is a common finding in newborns. Ketone bodies serve as an indispensable source of energy for extrahepatic tissues, especially the brain and lung of developing mammals. Another important function of ketone bodies is to provide acetoacetyl-CoA and acetyl-CoA for the synthesis of cholesterol, fatty acids, and complex lipids. During the early postnatal period, acetoacetate (AcAc) and beta-hydroxybutyrate are preferred over glucose as substrates for synthesis of phospholipids and sphingolipids in accord with requirements for brain growth and myelination. Thus, during the first 2 weeks of postnatal development, when the accumulation of cholesterol and phospholipids accelerates, the proportion of ketone bodies incorporated into these lipids increases. On the other hand, an increased proportion of ketone bodies is utilized for cerebroside synthesis during the period of active myelination. In the lung, AcAc serves better than glucose as a precursor for the synthesis of lung phospholipids. The synthesized lipids, particularly dipalmitoylphosphatidylcholine, are incorporated into surfactant, and thus have a potential role in supplying adequate surfactant lipids to maintain lung function during the early days of life (PMID: 3884391). 3-Hydroxybutyric acid is found to be associated with fumarase deficiency and medium-chain acyl-CoA dehydrogenase deficiency, which are inborn errors of metabolism.


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3α,7α-Dihydroxycoprostanic acid

3α,7α-Dihydroxycoprostanic acid is a bile acid excreted in small amounts in the urine of healthy subjects (PMID: 864325). 3α,7α-Dihydroxycoprostanic acid is the precursor to chenodeoxycholic acid, a bile acid. Bile acids are steroid acids found predominantly in the bile of mammals. The distinction between different bile acids is minute, depending only on the 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.
Showing 181 - 200 of 55724 compounds