Abstract
Taurine (aminoethane sulfonic acid) is an ubiquitous compound, found in very high concentrations in heart and muscle. Although taurine is classified as an amino acid, it does not participate in peptide bond formation. Nonetheless, the amino group of taurine is involved in a number of important conjugation reactions as well as in the scavenging of hypochlorous acid. Because taurine is a fairly inert compound, it is an ideal modulator of basic processes, such as osmotic pressure, cation homeostasis, enzyme activity, receptor regulation, cell development and cell signalling. The present review discusses several physiological functions of taurine. First, the observation that taurine depletion leads to the development of a cardiomyopathy indicates a role for taurine in the maintenance of normal contractile function. Evidence is provided that this function of taurine is mediated by changes in the activity of key Ca2+ transporters and the modulation Ca2+ sensitivity of the myofibrils. Second, in some species, taurine is an established osmoregulator, however, in mammalian heart the osmoregulatory function of taurine has recently been questioned. Third, taurine functions as an indirect regulator of oxidative stress. Although this action of taurine has been widely discussed, its mechanism of action is unclear. A potential mechanism for the antioxidant activity of taurine is discussed. Fourth, taurine stabilizes membranes through direct interactions with phospholipids. However, its inhibition of the enzyme, phospholipid N-methyltransferase, alters the phosphatidylcholine and phosphatidylethanolamine content of membranes, which in turn affects the function of key proteins within the membrane. Finally, taurine serves as a modulator of protein kinases and phosphatases within the cardiomyocyte. The mechanism of this action has not been studied. Taurine is a chemically simple compound, but it has profound effects on cells. This has led to the suggestion that taurine is an essential or semi-essential nutrient for many mammals.
Highlights
Taurine is an ubiquitous sulfur-containing, b-amino acid, which is considered an essential nutrient in some species [1]
According to Kocsis et al [3], a correlation exists between taurine levels and heart rate, with the highest taurine levels found in species with the
The physiological actions of taurine were studied using a model of taurine depletion mediated by taurine transport inhibitors or a model of nutritional depletion in cats
Summary
Taurine is an ubiquitous sulfur-containing, b-amino acid, which is considered an essential nutrient in some species [1]. Taurine loss during apoptotis has an adverse effect on the cell, the loss of taurine during a normal regulatory volume decrease can benefit the hyperosmotically stressed cell by serving as a safety valve to prevent membrane damage caused by excessive cell swelling This occurs in the ischemic heart, which accumulates osmolytes, such as lactate, phosphate and sodium. Based on the potential role of 5-taurinomethyluridine in modulating mitochondrial protein synthesis, Schaffer et al [8] proposed a mechanism for the regulation of reactive oxygen species production by taurine They predict that diminished rates of 5-taurinomethyluridine arising from taurine deficiency reduce the expression of mitochondrial encoded proteins. The protein kinases affecting these phosphoproteins as well as the importance of these phosphorylation changes in the taurine transporter knockout mice remain to be determined
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