Taurine

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Taurine (from taurus = bull, as it was discovered in ox (Bos taurus) bile) or 2-aminoethanesulfonic acid is an acidic chemical substance found in high abundance in the tissues of many animals/metazoa. Taurine is also found in plants, fungi, and some bacterial species, but in far less abundance. It is an amine with a sulfonic acid functional group, but it is not an amino acid in the biological sense, not being one of the twenty protein-forming compounds encoded by the universal genetic code. Small polypeptides have been identified as containing taurine, but to date there has been no report of a transfer RNA that is specifically charged with taurine.

Biosynthesis

The major pathway for mammalian taurine synthesis occurs in the liver via the cysteine sulfinic acid pathway. In this pathway, the sulfhydryl group of cysteine is first oxidized to cysteine sulfinic acid by the enzyme cysteine dioxygenase. Cysteine sulfinic acid, in turn, is decarboxylated by cysteine sulfinic acid decarboxylase to form hypotaurine. It is unclear whether hypotaurine is then spontaneously or enzymatically oxidized to yield taurine.

Physiological Roles

Taurine has two well documented physiological roles:

• For many animals/metazoa, taurine is among the major intracellular osmolytes and is thus an important contributor to the regulation of cell volume.

• Taurine is conjugated via its amino terminal group with the bile acids chenodeoxycholic acid and cholic acid to form the bile salts sodium taurochenodeoxycholate and sodium taurocholate (see bile). The low pKa (1.5) of taurine's sulfonic acid group ensures that this moiety is negatively charged in the pH ranges normally found in the intestinal tract and thus improves the surfactant properties of the cholic acid conjugate.

Taurine has also been implicated in a wide array of other physiological phenomena including inhibitory neurotransmission, long-term potentiation in the striatum/hippocampus, membrane stabilization, feedback inhibition of neutrophil/macrophage respiratory bursts, and calcium homeostasis. The evidence for these claims, when compared against that reported for taurine's role in bile acid synthesis and osmoregulation, is relatively poor.

Premature born infants who lack the enzymes needed to convert cystathione to cysteine may become deficient in taurine. Thus, taurine is a dietary essential nutrient in these individuals.

There is also evidence that excess taurine in adults causes hypertension. However, its positive and negative effects in humans have not been fully documented.

Commercial uses for taurine

Over recent years, taurine has become a common ingredient in high-caffeine energy drinks. Perhaps the most popular of these drinks is Red Bull, but others include AMP Energy Drink (made by Mountain Dew), Rockstar, Full Throttle (Coca-Cola), Monster, Tab Energy Drink, and Sobe Adrenaline Rush.

It is also found in some contact lens cleaning solutions, such as Amo Complete Moisture Plus.de:Taurin es:Taurina fr:Taurine hu:Taurin nl:Taurine ja:タウリン pl:Tauryna sl:Tavrin fi:Tauriini zh:牛磺酸