The Possible Essentiality of Taurine

Taurine is a dietary essential in the cat, which is an obligate carnivore with a limited capacity for taurine synthesis from cysteine. On a taurine-free diet, neither supplementary methionine nor cysteine will maintain normal plasma concentrations of taurine, because cats have an alternative pathway of cysteine metabolism reaction with mevalonic acid to yield felinine (3-hydroxy-1,1-dimethylpropyl-cysteine), which is excreted in the urine. The activity of cysteine sulfinic acid decarboxylase in cat liver is very low. 

It is not known to what extent taurine may be a dietary essential for human beings. There is little cysteine sulfinic acid decarboxylase activity in the human liver and, like the cat, loading doses of methionine and cysteine do not result in any significant increase in plasma taurine. This may be because cysteine sulfinic acid can also undergo transamination to /3-sulfhydryl pyruvate, which then loses sulfur dioxide nonenzymically to form pyruvate, thus regulating the amount of taurine that is formed from cysteine. There is no evidence of the development of any taurine deficiency disease under normal conditions. 

There are very few plant sources of taurine, and strict vegetarians have a very low intake of preformed taurine. Nevertheless, the plasma concentration 

In children undergoing long-term total parenteral nutrition without taurine supplements, there are changes in the electroretinogram similar to those seen in the taurine-deficient cat, suggesting that there is a requirement for some preformed taurine and that endogenous synthesis may be inadequate. 

It has been suggested that preterm infants may require a dietary source of preformed taurine breast mifk initially contains a high concentration (about 300 /xmol per L), and breast-fed infants maintain a higher plasma concentration of taurine than those fed on formula without added taurine (Chesney et al., 1998). Although mUk from vegan mothers has a low concentration of taurine, and their infants have lower plasma concentrations and urinary excretion of taurine than the infants of omnivore mothers, there is no evidence that (full-term) infants of vegan mothers show any signs of taurine deficiency. 

1-dimethylpropyl-cysteine), which is excreted in the urine. The activity of cysteine sulfinic acid dectuboxylase in cat liver is very low. 

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