Chemistry:Taurine

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Short description: Aminosulfonic acid not incorporated into proteins
Taurine
Taurin.svg
Taurine-from-xtal-Mercury-3D-balls.png
Names
Preferred IUPAC name
2-Aminoethanesulfonic acid
Other names
Tauric acid
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
KEGG
UNII
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).
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Infobox references

Taurine (/ˈtɔːriːn/), or 2-aminoethanesulfonic acid, is a non-proteinogenic 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 dietary nutrient and is not included among nutrients with a recommended intake level.[4] Taurine is commonly sold as a dietary supplement, but there is no good clinical evidence that taurine supplements provide any benefit to human health.[5] Taurine is used as a food additive for cats, dogs, and poultry.[6]

Taurine concentrations in land plants are low or undetectable, but up to 1,000 nmol/g wet weight have been found in algae.[7][8]

Chemical and biochemical features

Taurine exists as a zwitterion H
3N+
CH
2CH
2SO−
3, as verified by X-ray crystallography.[9] The sulfonic acid has a low pKa[10] ensuring that it is fully ionized to the sulfonate at the pHs found in the intestinal tract.

Synthesis

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.[11]

In 1993, about 5,000–6,000 tonnes of taurine were produced for commercial purposes: 50% for pet food and 50% in pharmaceutical applications.[12] 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 3,000 tonnes.[13]

In the laboratory, taurine can be produced by alkylation of ammonia with bromoethanesulfonate salts.[14]

Biosynthesis

Taurine is naturally derived from cysteine. Mammalian taurine synthesis occurs in the pancreas 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.[15]

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.[16]

A pathway for taurine biosynthesis from serine and sulfate is reported in microalgae,[8] developing chicken embryos,[17] and chick liver.[18] 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.

Oxidative degradation of cysteine to taurine

In food

Taurine occurs naturally in fish and meat.[5][19][20] The mean daily intake from omnivore diets was determined to be around 58 mg (range from 9–372 mg),[21] and to be low or negligible from a vegan diet.[5] Typical taurine consumption in the American diet is about 123–178 mg per day.[5]

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 on taurine and can easily become deficient. Either raw feeding or addition of extra taurine can satisfy this requirement.[22][23]

Lysine and taurine can both mask the metallic flavor of potassium chloride, a salt substitute.[24]

Breast milk

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.[25]

Energy drinks and dietary supplements

Taurine is an ingredient in some energy drinks in amounts of 1–3 grams per serving.[5][26][27][28] A 1999 assessment of European consumption of energy drinks found that taurine intake was 40-400 mg per day.[21]

Research

Taurine is not regarded as an essential 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.[5] Preliminary human studies on the possible effects of taurine supplementation have been inadequate due to low subject numbers, inconsistent designs, and variable doses.[5]

Safety and toxicity

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.[6] Other sources indicate that taurine is safe for supplemental intake in normal healthy adults at up to 3 grams per day.[5][29]

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".[30]

Animal dietary requirement

Cats

Cats lack the enzymatic machinery (sulfinoalanine decarboxylase) to produce taurine and must therefore acquire it from their diet.[31] A taurine deficiency in cats can lead to retinal degeneration and eventually blindness – a condition known as central retinal degeneration (CRD),[32][33] as well as hair loss and tooth decay. Other effects of a diet lacking in this essential amino acid are dilated cardiomyopathy and reproductive failure in female cats.[34]

Decreased plasma taurine concentration has been demonstrated to be associated with feline dilated cardiomyopathy. Unlike CRD, the condition is reversible with supplementation. [35]

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.[36] Studies suggest the amino acid should be supplied at 10 mg/kg of bodyweight/day for domestic cats.[37]

Other mammals

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.[38]

Birds

Taurine appears essential to 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.[39]

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.[40]

Fish

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.[41]

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.[42]

Derivatives

  • Taurine is used in the preparation of the anthelmintic drug netobimin (Totabin).
  • Taurolidine
  • Taurocholic acid and tauroselcholic acid
  • Tauromustine
  • 5-Taurinomethyluridine and 5-taurinomethyl-2-thiouridine are modified uridines in (human) mitochondrial tRNA.[43]
  • Tauryl is the functional group attaching at the sulfur, 2-aminoethylsulfonyl.[44]
  • Taurino is the functional group attaching at the nitrogen, 2-sulfoethylamino.
  • Thiotaurine

See also

References

  1. ↑ "Taurine: new implications for an old amino acid". FEMS Microbiology Letters 226 (2): 195–202. September 2003. doi:10.1016/S0378-1097(03)00611-6. PMID 14553911. 
  2. ↑ "Einige neue Bestandtheile der Galle des Ochsen". Annalen der Physik 85 (2): 326–337. 1827. doi:10.1002/andp.18270850214. Bibcode: 1827AnP....85..326T. https://zenodo.org/record/1423514. 
  3. ↑ "Bringing Together Academic and Industrial Chemistry: Edmund Ronald' Contribution". Substantia 3 (1): 139–152. 2019. 
  4. ↑ 4.0 4.1 "Daily Value on the New Nutrition and Supplement Facts Labels". US Food and Drug Administration. 25 February 2022. https://www.fda.gov/food/new-nutrition-facts-label/daily-value-new-nutrition-and-supplement-facts-labels#referenceguide. 
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 "Taurine". Drugs.com. 15 May 2023. https://www.drugs.com/npp/taurine.html. 
  6. ↑ 6.0 6.1 EFSA Panel on Additives and Products or Substances used in Animal Feed (2012). "Scientific Opinion on the safety and efficacy of taurine as a feed additive for all animal species". EFSA Journal 10 (6): 2736. doi:10.2903/j.efsa.2012.2736. 
  7. ↑ "Occurrence of Taurine in Plants". Agricultural and Biological Chemistry 50 (7): 1887–1888. 1986. doi:10.1271/bbb1961.50.1887. https://www.jstage.jst.go.jp/article/bbb1961/50/7/50_7_1887/_article. 
  8. ↑ 8.0 8.1 "Amino acid content of selected plant, algae and insect species: a search for alternative protein sources for use in pet foods" (in en). Journal of Nutritional Science 3: e39. 2014. doi:10.1017/jns.2014.33. ISSN 2048-6790. PMID 26101608. 
  9. ↑ "Taurine". Acta Crystallographica Section C 56 (1): e23–e24. 2000. doi:10.1107/S0108270199016029. Bibcode: 2000AcCrC..56E..23G. 
  10. ↑ "13C nuclear magnetic resonance study of the complexation of calcium by taurine". Journal of Inorganic Biochemistry 13 (2): 137–150. October 1980. doi:10.1016/S0162-0134(00)80117-8. PMID 7431022. 
  11. ↑ "Ullmann's Encyclopedia of Industrial Chemistry". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. 2000. doi:10.1002/14356007.a25_503. 
  12. ↑ Tully PS, ed (2000). "Sulfonic Acids". Kirk-Othmer Encyclopedia of Chemical Technology. John Wiley & Sons, Inc. doi:10.1002/0471238961.1921120620211212.a01. ISBN 978-0-471-23896-6. 
  13. ↑ Amanda Xia (2010-01-03). "China Taurine Market Is Expected To Recover". Press release and article directory: technology. http://uberarticles.com/miscellaneous/china-taurine-market-is-expected-to-recover/. 
  14. ↑ "Taurine". Organic Syntheses 18: 77. 1938. doi:10.15227/orgsyn.018.0077. 
  15. ↑ "Oxidation of hypotaurine in rat liver". Biochimica et Biophysica Acta 63: 210–212. September 1962. doi:10.1016/0006-3002(62)90357-8. PMID 13979247. 
  16. ↑ "Review: taurine: a "very essential" amino acid". Molecular Vision 18: 2673–2686. 2012. PMID 23170060. 
  17. ↑ "The Utilization of Sulfate Sulfur for the Synthesis of Taurine in the Developing Chick Embryo". Journal of Biological Chemistry 212 (1): 469–475. 1955. doi:10.1016/s0021-9258(18)71134-4. ISSN 0021-9258. PMID 13233249. 
  18. ↑ "The Synthesis of Taurine from Sulfate III. Further Evidence for the Enzymatic Pathway in Chick Liver" (in en). Experimental Biology and Medicine 139 (3): 755–761. 1972-03-01. doi:10.3181/00379727-139-36232. ISSN 1535-3702. PMID 5023763. http://ebm.sagepub.com/lookup/doi/10.3181/00379727-139-36232. 
  19. ↑ "The sulfur-containing amino acids: an overview". The Journal of Nutrition 136 (6 Suppl): 1636S–1640S. June 2006. doi:10.1093/jn/136.6.1636S. PMID 16702333. 
  20. ↑ "Physiological actions of taurine". Physiological Reviews 72 (1): 101–163. January 1992. doi:10.1152/physrev.1992.72.1.101. PMID 1731369. 
  21. ↑ 21.0 21.1 "Opinion on Caffeine, Taurine and D-Glucurono – g -Lactone as constituents of so-called 'energy' drinks". Directorate-General Health and Consumers, European Commission, European Union. 1999-01-21. http://ec.europa.eu/food/fs/sc/scf/out22_en.html. 
  22. ↑ "Rhodopsin topography and rod-mediated function in cats with the retinal degeneration of taurine deficiency". Experimental Eye Research 45 (4): 481–490. October 1987. doi:10.1016/S0014-4835(87)80059-3. PMID 3428381. 
  23. ↑ Spitze, A. R.; Wong, D. L.; Rogers, Q. R.; Fascetti, A. J. (2003). "Taurine concentrations in animal feed ingredients; cooking influences taurine content". J. Anim. Physiol. a. Anim. Nutr. 87: 251–262. https://www.vetmed.ucdavis.edu/sites/g/files/dgvnsk491/files/aal/pdfs/spitze.pdf. Retrieved January 27, 2024. 
  24. ↑ dos Santos, Bibiana Alves; Campagnol, Paulo Cezar Bastianello; Morgano, Marcelo Antônio; Pollonio, Marise Aparecida Rodrigues (January 2014). "Monosodium glutamate, disodium inosinate, disodium guanylate, lysine and taurine improve the sensory quality of fermented cooked sausages with 50% and 75% replacement of NaCl with KCl". Meat Science 96 (1): 509–513. doi:10.1016/j.meatsci.2013.08.024. 
  25. ↑ "Taurine in neonatal nutrition – revisited". Archives of Disease in Childhood. Fetal and Neonatal Edition 89 (6): F473–474. November 2004. doi:10.1136/adc.2004.055095. PMID 15499132. 
  26. ↑ "Original Rockstar Ingredients". http://www.rockstar69.com/productIngredients.php?pdt=1. 
  27. ↑ "Nos Energy Drink – Review". energyfanatics.com. 2008-05-03. http://energyfanatics.com/2008/05/03/nos-energy-drink-review/. 
  28. ↑ "Taurine in sports and exercise". Journal of the International Society of Sports Nutrition 18 (39): 39. 2021. doi:10.1186/s12970-021-00438-0. PMID 34039357. 
  29. ↑ "Risk assessment for the amino acids taurine, L-glutamine and L-arginine". Regulatory Toxicology and Pharmacology 50 (3): 376–399. April 2008. doi:10.1016/j.yrtph.2008.01.004. PMID 18325648. "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 Tau at supplemental intakes up to 3 g/d, Gln at intakes up to 14 g/d and Arg at intakes up to 20 g/d, and these levels are identified as the respective OSLs for normal healthy adults.". 
  30. ↑ "Safety issues associated with commercially available energy drinks". Journal of the American Pharmacists Association 48 (3): e55–63; quiz e64–67. 2008. doi:10.1331/JAPhA.2008.07055. PMID 18595815. 
  31. ↑ "Taurine: an essential nutrient for the cat". The Journal of Nutrition 108 (5): 773–778. May 1978. doi:10.1093/jn/108.5.773. PMID 641594. https://www.researchgate.net/publication/22499901. 
  32. ↑ "Taurine And Its Importance In Cat Foods". Iams Cat Nutrition Library. 2004. http://www.iams.com/en_BI/jhtmls/nutrition/sw_NutritionQuestions_qanswer.jhtml?li=en_BI&sc=C&bc=I&pti=PN&qi=2169. 
  33. ↑ "Nutrient Requirements of Cats". Nutrient Requirements of Cats, Revised Edition, 1986. 1986. http://newton.nap.edu/catalog/910.html. 
  34. ↑ "Retinal degeneration associated with taurine deficiency in the cat". Science 188 (4191): 949–951. May 1975. doi:10.1126/science.1138364. PMID 1138364. Bibcode: 1975Sci...188..949H. 
  35. ↑ "Myocardial failure in cats associated with low plasma taurine: a reversible cardiomyopathy". Science 237 (4816): 764–768. August 1987. doi:10.1126/science.3616607. PMID 3616607. Bibcode: 1987Sci...237..764P. 
  36. ↑ "AAFCO Cat Food Nutrient Profiles". http://maxshouse.com/nutrition/aafco_cat_food_nutrient_profiles.htm. 
  37. ↑ "The taurine requirement of the adult cat". Journal of Small Animal Practice 23 (9): 533–537. 1982. doi:10.1111/j.1748-5827.1982.tb02514.x. 
  38. ↑ Schaffer, Stephen W.; Ito, Takashi; Azuma, Junichi (January 2014). "Clinical significance of taurine". Amino Acids 46 (1): 1–5. doi:10.1007/s00726-013-1632-8.  (abstracts of animal citations used to provide list of species)
  39. ↑ "Parental prey selection affects risk-taking behaviour and spatial learning in avian offspring". Proceedings of the Royal Society B: Biological Sciences 274 (1625): 2563–2569. October 2007. doi:10.1098/rspb.2007.0687. PMID 17698490. 
  40. ↑ Surai, P.F.; Kochish, I.I.; Kidd, M.T. (February 2020). "Taurine in poultry nutrition". Animal Feed Science and Technology 260: 114339. doi:10.1016/j.anifeedsci.2019.114339. 
  41. ↑ Salze, Guillaume P.; Davis, D. Allen (February 2015). "Taurine: a critical nutrient for future fish feeds". Aquaculture 437: 215–229. doi:10.1016/j.aquaculture.2014.12.006. 
  42. ↑ Sampath, W. W. H. A.; Rathnayake, R. M. D. S.; Yang, Mengxi; Zhang, Wenbing; Mai, Kangsen (November 2020). "Roles of dietary taurine in fish nutrition". Marine Life Science & Technology 2 (4): 360–375. doi:10.1007/s42995-020-00051-1. https://www.researchgate.net/publication/343025001. 
  43. ↑ "Taurine as a constituent of mitochondrial tRNAs: new insights into the functions of taurine and human mitochondrial diseases". The EMBO Journal 21 (23): 6581–6589. December 2002. doi:10.1093/emboj/cdf656. PMID 12456664. 
  44. ↑ Systematic nomenclature of organic, organometallic and coordination chemistry. EPFL Press. 2007. p. 226. ISBN 978-1-4200-4615-1. 



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