Names | |
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Preferred IUPAC name 2-Aminoethanesulfonic acid | |
Other names Tauric acid | |
Identifiers | |
3D model (JSmol) | |
ChEBI | |
ChEMBL | |
ChemSpider | |
DrugBank | |
ECHA InfoCard | 100.003.168 |
KEGG | |
PubChem CID | |
UNII | |
CompTox Dashboard (EPA) | |
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Properties | |
C2H7NO3S | |
Molar mass | 125.14 g/mol |
Appearance | colorless or white solid |
Density | 1.734 g/cm3 (at −173.15 °C) |
Melting point | 305.11 °C (581.20 °F; 578.26 K) Decomposes into simple molecules |
Acidity (pKa) | <0, 9.06 |
Related compounds | |
Related compounds | Sulfamic acid Aminomethanesulfonic acid Homotaurine |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Taurine ( /ˈtɔːriːn/ ), or 2-aminoethanesulfonic acid, is a non-proteinogenic naturally occurring amino sulfonic acid that is widely distributed in animal tissues. [1] It is a major constituent of bile and can be found in the large intestine, and accounts for up to 0.1% of total human body weight.
Taurine is named after Latin taurus (cognate to Ancient Greek ταῦρος, taûros) meaning bull or ox, as it was first isolated from ox bile in 1827 by German scientists Friedrich Tiedemann and Leopold Gmelin. [2] It was discovered in human bile in 1846 by Edmund Ronalds. [3]
Although taurine is abundant in human organs with diverse putative roles, it is not an essential human dietary nutrient and is not included among nutrients with a recommended intake level. [4] Taurine is synthesized naturally in the human liver from methionine and cysteine. [5]
Taurine is commonly sold as a dietary supplement, but there is no good clinical evidence that taurine supplements provide any benefit to human health. [6] Taurine is used as a food additive for cats (who require it as an essential nutrient), dogs, and poultry. [7]
Taurine concentrations in land plants are low or undetectable, but up to 1000 nmol/g wet weight have been found in algae. [8] [9]
Taurine exists as a zwitterion H3N+CH2CH2SO−3, as verified by X-ray crystallography. [10] The sulfonic acid has a low pKa [11] ensuring that it is fully ionized to the sulfonate at the pHs found in the intestinal tract.
Synthetic taurine is obtained by the ammonolysis of isethionic acid (2-hydroxyethanesulfonic acid), which in turn is obtained from the reaction of ethylene oxide with aqueous sodium bisulfite. A direct approach involves the reaction of aziridine with sulfurous acid. [12]
In 1993, about 5000–6000 tonnes of taurine were produced for commercial purposes: 50% for pet food and 50% in pharmaceutical applications. [13] As of 2010, China alone has more than 40 manufacturers of taurine. Most of these enterprises employ the ethanolamine method to produce a total annual production of about 3000 tonnes. [14]
In the laboratory, taurine can be produced by alkylation of ammonia with bromoethanesulfonate salts. [15]
Taurine is naturally derived from cysteine. Mammalian taurine synthesis occurs in the liver via the cysteine sulfinic acid pathway. In this pathway, cysteine is first oxidized to its sulfinic acid, catalyzed by the enzyme cysteine dioxygenase. Cysteine sulfinic acid, in turn, is decarboxylated by sulfinoalanine decarboxylase to form hypotaurine. Hypotaurine is enzymatically oxidized to yield taurine by hypotaurine dehydrogenase. [16]
Taurine is also produced by the transsulfuration pathway, which converts homocysteine into cystathionine. The cystathionine is then converted to hypotaurine by the sequential action of three enzymes: cystathionine gamma-lyase, cysteine dioxygenase, and cysteine sulfinic acid decarboxylase. Hypotaurine is then oxidized to taurine as described above. [17]
A pathway for taurine biosynthesis from serine and sulfate is reported in microalgae, [9] developing chicken embryos, [18] and chick liver. [19] Serine dehydratase converts serine to 2-aminoacrylate, which is converted to cysteic acid by 3′-phosphoadenylyl sulfate:2-aminoacrylate C-sulfotransferase. Cysteic acid is converted to taurine by cysteine sulfinic acid decarboxylase.
Taurine occurs naturally in fish and meat. [6] [20] [21] The mean daily intake from omnivore diets was determined to be around 58 mg (range 9–372 mg), [22] and to be low or negligible from a vegan diet. [6] Typical taurine consumption in the American diet is about 123–178 mg per day. [6]
Taurine is partially destroyed by heat in processes such as baking and boiling. This is a concern for cat food, as cats have a dietary requirement for taurine and can easily become deficient. Either raw feeding or supplementing taurine can satisfy this requirement. [23] [24]
Both lysine and taurine can mask the metallic flavor of potassium chloride, a salt substitute. [25]
Prematurely born infants are believed to lack the enzymes needed to convert cystathionine to cysteine, and may, therefore, become deficient in taurine. Taurine is present in breast milk, and has been added to many infant formulas as a measure of prudence since the early 1980s. However, this practice has never been rigorously studied, and as such it has yet to be proven to be necessary, or even beneficial. [26]
Taurine is an ingredient in some energy drinks in amounts of 1–3 g per serving. [6] [27] [28] [29] A 1999 assessment of European consumption of energy drinks found that taurine intake was 40–400 mg per day. [22] [ clarification needed ]
Taurine is not regarded as an essential human dietary nutrient and has not been assigned recommended intake levels. [4] High-quality clinical studies to determine possible effects of taurine in the body or following dietary supplementation are absent from the literature. [6] Preliminary human studies on the possible effects of taurine supplementation have been inadequate due to low subject numbers, inconsistent designs, and variable doses. [6] Preliminary studies have suggested that supplementing with taurine may increase exercise capacity [30] [31] [32] and affects lipid profiles in individuals with diabetes. [33] [34]
According to the European Food Safety Authority, taurine is "considered to be a skin and eye irritant and skin sensitiser, and to be hazardous if inhaled;" it may be safe to consume up to 6 grams of taurine per day. [7] Other sources indicate that taurine is safe for supplemental intake in normal healthy adults at up to 3 grams per day. [6] [35]
A 2008 review found no documented reports of negative or positive health effects associated with the amount of taurine used in energy drinks, concluding, "The amounts of guarana, taurine, and ginseng found in popular energy drinks are far below the amounts expected to deliver either therapeutic benefits or adverse events". [36]
Cats lack the enzymatic machinery (sulfinoalanine decarboxylase) to produce taurine and must therefore acquire it from their diet. [37] A taurine deficiency in cats can lead to retinal degeneration and eventually blindness – a condition known as central retinal degeneration [38] [39] as well as hair loss and tooth decay. Other effects of a diet lacking in this essential amino acid are dilated cardiomyopathy [40] , and reproductive failure in female cats[ citation needed ].
Decreased plasma taurine concentration has been demonstrated to be associated with feline dilated cardiomyopathy. Unlike CRD, the condition is reversible with supplementation. [41]
Taurine is now a requirement of the Association of American Feed Control Officials (AAFCO) and any dry or wet food product labeled approved by the AAFCO should have a minimum of 0.1% taurine in dry food and 0.2% in wet food. [42] Studies suggest the amino acid should be supplied at 10 mg per kilogram of bodyweight per day for domestic cats. [43]
A number of other mammals also have a requirement for taurine. While the majority of dogs can synthesize taurine, case reports have described a singular American cocker spaniel, 19 Newfoundland dogs, and a family of golden retrievers suffering from taurine deficiency treatable with supplementation. Foxes on fur farms also appear to require dietary taurine. The rhesus, cebus and cynomolgus monkeys each require taurine at least in infancy. The giant anteater also requires taurine. [44]
Taurine appears to be essential for the development of passerine birds. Many passerines seek out taurine-rich spiders to feed their young, particularly just after hatching. Researchers compared the behaviours and development of birds fed a taurine-supplemented diet to a control diet and found the juveniles fed taurine-rich diets as neonates were much larger risk takers and more adept at spatial learning tasks. Under natural conditions, each blue tit nestling receive 1 mg of taurine per day from parents. [45]
Taurine can be synthesized by chickens. Supplementation has no effect on chickens raised under adequate lab conditions, but seems to help with growth under stresses such as heat and dense housing. [46]
Species of fish, mostly carnivorous ones, show reduced growth and survival when the fish-based feed in their food is replaced with soy meal or feather meal. Taurine has been identified as the factor responsible for this phenomenon; supplementation of taurine to plant-based fish feed reverses these effects. Future aquaculture is expected to use more of these more environmentally-friendly protein sources, so supplementation would become more important. [47]
The need of taurine in fish is conditional, differing by species and growth stage. The Olive flounder, for example, has lower capacity to synthesize taurine compared to the rainbow trout. Juvenile fish are less efficient at taurine biosyntheis due to reduced cysteine sulfinate decarboxylase levels. [48]
Cysteine is a semiessential proteinogenic amino acid with the formula HOOC−CH(−NH2)−CH2−SH. The thiol side chain in cysteine often participates in enzymatic reactions as a nucleophile. Cysteine is chiral, but both D and L-cysteine are found in nature. L‑Cysteine is a protein monomer in all biota, and D-cysteine acts as a signaling molecule in mammalian nervous systems. Cysteine is named after its discovery in urine, which comes from the urinary bladder or cyst, from Greek κύστη kýsti, "bladder".
Pantothenic acid (vitamin B5) is a B vitamin and an essential nutrient. All animals need pantothenic acid in order to synthesize coenzyme A (CoA), which is essential for cellular energy production and for the synthesis and degradation of proteins, carbohydrates, and fats.
Methionine is an essential amino acid in humans.
A nutrient is a substance used by an organism to survive, grow and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi and protists. Nutrients can be incorporated into cells for metabolic purposes or excreted by cells to create non-cellular structures such as hair, scales, feathers, or exoskeletons. Some nutrients can be metabolically converted into smaller molecules in the process of releasing energy such as for carbohydrates, lipids, proteins and fermentation products leading to end-products of water and carbon dioxide. All organisms require water. Essential nutrients for animals are the energy sources, some of the amino acids that are combined to create proteins, a subset of fatty acids, vitamins and certain minerals. Plants require more diverse minerals absorbed through roots, plus carbon dioxide and oxygen absorbed through leaves. Fungi live on dead or living organic matter and meet nutrient needs from their host.
An essential amino acid, or indispensable amino acid, is an amino acid that cannot be synthesized from scratch by the organism fast enough to supply its demand, and must therefore come from the diet. Of the 21 amino acids common to all life forms, the nine amino acids humans cannot synthesize are valine, isoleucine, leucine, methionine, phenylalanine, tryptophan, threonine, histidine, and lysine.
A dietary supplement is a manufactured product intended to supplement a person's diet by taking a pill, capsule, tablet, powder, or liquid. A supplement can provide nutrients either extracted from food sources, or that are synthetic. The classes of nutrient compounds in supplements include vitamins, minerals, fiber, fatty acids, and amino acids. Dietary supplements can also contain substances that have not been confirmed as being essential to life, and so are not nutrients per se, but are marketed as having a beneficial biological effect, such as plant pigments or polyphenols. Animals can also be a source of supplement ingredients, such as collagen from chickens or fish for example. These are also sold individually and in combination, and may be combined with nutrient ingredients. The European Commission has also established harmonized rules to help insure that food supplements are safe and appropriately labeled.
Cat food is food specifically formulated and designed for consumption by cats. As obligate carnivores, cats have specific requirements for their dietary nutrients, namely nutrients found only in meat or synthesized, such as taurine and Vitamin A. Certain nutrients, including many vitamins and amino acids, are degraded by the temperatures, pressures and chemical treatments used during manufacture, and hence must be added after manufacture to avoid nutritional deficiency. Cat food is typically sold as dry kibble, or as wet food in cans and pouches.
Cysteine dioxygenase (CDO) is a non-heme iron enzyme that catalyzes the conversion of L-cysteine to cysteine sulfinic acid. CDO plays an important role in cysteine catabolism, regulating intracellular levels of cysteine and responding changes in cysteine availability. As such, CDO is highly regulated and undergoes large changes in concentration and efficiency. It oxidizes cysteine to the corresponding sulfinic acid by activation of dioxygen, although the exact mechanism of the reaction is still unclear. In addition to being found in mammals, CDO also exists in some yeast and bacteria, although the exact function is still unknown. CDO has been implicated in various neurodegenerative diseases and cancers, which is likely related to cysteine toxicity.
Raw feeding is the practice of feeding domestic dogs, cats, and other animals a diet consisting primarily of uncooked meat, edible bones, and organs. The ingredients used to formulate raw diets vary. Some pet owners choose to make home-made raw diets to feed their animals but commercial raw diets are also available.
Pet food is animal feed intended for consumption by pets. Typically sold in pet stores and supermarkets, it is usually specific to the type of animal, such as dog food or cat food. Most meat used for animals is a byproduct of the human food industry, and is not regarded as "human grade". Examples of foods for pets would be canned foods and dry mix. Pet food production has environmental, land-use and climate change impacts.
Proteins are essential nutrients for the human body. They are one of the building blocks of body tissue and can also serve as a fuel source. As a fuel, proteins provide as much energy density as carbohydrates: 17 kJ per gram; in contrast, lipids provide 37 kJ per gram. The most important aspect and defining characteristic of protein from a nutritional standpoint is its amino acid composition.
Cystathionine is an intermediate in the synthesis of cysteine from homocysteine. It is produced by the transsulfuration pathway and is converted into cysteine by cystathionine gamma-lyase (CTH).
The enzyme sulfinoalanine decarboxylase (EC 4.1.1.29) catalyzes the chemical reaction
Cysteine sulfinic acid is the organic compound with the nominal formula HO2SCH2CH(NH2)CO2H. It is a rare example of an amino acid bearing a sulfinic acid functional group. It is a white solid that is soluble in water. Like most natural amino acids, it is chiral, only the L-enantiomer occurs in nature, and it exists as the zwitterion at neutral pH. It is an intermediate in cysteine metabolism. It is not a coded amino acid, but is produced post-translationally. Peptides containing the cysteine sulfinic acid residue are substrates for cysteine sulfinic acid reductase.
A low-sulfur diet is a diet with reduced sulfur content. Important dietary sources of sulfur and sulfur containing compounds may be classified as essential mineral, essential amino acid (methionine) and semi-essential amino acid.
Magnesium taurate, also known as magnesium ditaurate or magnesium taurinate, is the magnesium salt of taurine, and a mineral supplement.
Insect-based pet food is pet food consisting of, or containing insects digestible by pets such as dogs or cats. A limited, but growing number of products are available on the market, including insect-based cat food, dog food, and pet treats.
In general, cognitive support diets are formulated to include nutrients that have a known role in brain development, function and/or maintenance, with the goal of improving and preserving mental processes such as attentiveness, short-term and long-term memory, learning, and problem solving. Currently, there is very little conclusive research available regarding cat cognition as standardized tests for evaluating cognitive ability are less established and less reliable than cognitive testing apparatus used in other mammalian species, like dogs. Much of what is known about feline cognition has been inferred from a combination of owner-reported behaviour, brain necropsies, and comparative cognitive neurology of related animal models. Cognition claims appear primarily on kitten diets which include elevated levels of nutrients associated with optimal brain development, although there are now diets available for senior cats that include nutrients to help slow the progression of age-related changes and prevent cognitive decline. Cognition diets for cats contain a greater portion of omega-3 fatty acids, especially docosahexaenoic acid (DHA) as well as eicosapentaenoic acid (EPA), and usually feature a variety of antioxidants and other supporting nutrients thought to have positive effects on cognition.
As in the human practice of veganism, vegan dog foods are those formulated with the exclusion of ingredients that contain or were processed with any part of an animal, or any animal byproduct. Vegan dog food may incorporate the use of fruits, vegetables, cereals, legumes including soya, nuts, vegetable oils, as well as any other non-animal based foods.
Glutamate decarboxylase like 1 (GADL1) is the enzyme responsible for decarboxylating aspartate (Asp) to β-alanine and cysteine sulfinic acid (CSA) to hypotaurine. GADL1 is a Pyridoxal 5’-phosphate (PLP)-dependent enzyme. By decarboxylating Asp to β-alanine, GADL1 consequently plays a role in the production of carnosine. Carnosine and taurine have multiple biological functions such as calcium regulation, pH buffering, metal chelation, and antioxidant effects. β-Alanine also plays a role as neurotransmitter or neuromodulator in the central nervous system (CNS) and olfactory bulbs.
the newer method described as the Observed Safe Level (OSL) or Highest Observed Intake (HOI) was utilized. The OSL risk assessments indicate that based on the available published human clinical trial data, the evidence for the absence of adverse effects is strong for taurine at supplemental intakes up to 3 g/day, glutamine at intakes up to 14 g/day and arginine at intakes up to 20 g/day, and these levels are identified as the respective OSLs for normal healthy adults.