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Taurine

life science Maturity 11-13 Next article →

Taurine is a naturally occurring organic compound found throughout the animal kingdom. Chemically, it is known as a non-proteinogenic amino sulfonic acid. This specific name means that while it is similar to the amino acids used to build proteins, it is not actually used in protein synthesis. Instead, it is widely distributed in various mammalian tissues and organs. It is also a major component of bile, which helps with digestion.

Degradation of Cysteine to Taurine
Degradation of Cysteine to Taurine

In the human body, taurine is produced through several different biological pathways. The primary site for this production is the liver. One major method is the cysteine sulfinic acid pathway. In this process, the amino acid cysteine is first oxidized into sulfinic acid by an enzyme called cysteine dioxygenase. This sulfinic acid is then converted into hypotaurine by the enzyme sulfinoalanine decarboxylase. Finally, the enzyme hypotaurine dehydrogenase oxidizes the hypotaurine to create taurine.

Degradation of Cysteine to Taurine
Degradation of Cysteine to Taurine

Another way humans produce taurine is through the transsulfuration pathway. This pathway converts the amino acid homocysteine into cystathionine. Three different enzymes then work in sequence to turn cystathionine into hypotaurine. These enzymes are cystathionine gamma-lyase, cysteine dioxygenase, and cysteine sulfinic acid decarboxylase. Once hypotaurine is formed, it is oxidized into taurine just like in the first pathway. Microalgae and certain bird embryos use a different method involving serine and sulfate to create the compound.

The history of taurine began in 1827. Two German scientists, Friedrich Tiedemann and Leopold Gmelin, first isolated the substance from ox bile. In 1838, another German scientist named Von H. Demarcay gave it the common name "taurine." This name is derived from the Latin word "taurus," which means bull or ox. It took several more years for researchers to find it in humans. In 1846, Edmund Ronalds successfully identified taurine in human bile.

Taurine levels vary greatly depending on the food source. It is naturally abundant in animal tissues, particularly in meat and fish. For example, raw scallops contain 827 mg of taurine per 100 grams. Raw mussels contain 655 mg, while raw clams contain 520 mg. In contrast, plant-based foods like fruits, vegetables, grains, and nuts contain zero taurine. Because of this, a vegan diet typically provides low or negligible amounts of the compound.

Degradation of Cysteine to Taurine
Degradation of Cysteine to Taurine

While humans can make their own taurine, many animals cannot. Cats are a notable example because they lack the enzyme sulfinoalanine decarboxylase. Without this enzyme, cats cannot produce enough taurine and must get it from their diet. A deficiency in cats can lead to serious health issues like retinal degeneration, which causes blindness. It can also cause hair loss, tooth decay, and a heart condition called dilated cardiomyopathy. To prevent this, pet food must meet specific minimum requirements of taurine.

Other animals also show specific needs for this compound. Certain monkeys, such as the rhesus and cynomolgus, require taurine during infancy. Some birds, like the blue tit, also rely on it for development. These birds often feed their young spiders because spiders are rich in taurine. In the world of fish farming, adding taurine to plant-based feeds can help fish grow better. This is important because many carnivorous fish struggle to grow when they eat only soy or feather meal instead of fish-based protein.

Today, taurine is used in many commercial products. It is a common ingredient in many energy drinks, often appearing in amounts of 1,000 mg per serving. It is also sold as a dietary supplement. In 1993, about half of all commercially produced taurine was used for pet food, while the other half was used for pharmaceutical applications. While it is used in many places, scientists are still studying its exact role in human physiology. Currently, it is not considered an essential nutrient for humans because our bodies can synthesize it internally.

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