Taurine conjugation with bile acids

Taurine conjugation with bile acids, phenylacetic acid, and indolylacetic acid seems to be a minor process in most species, but in the pigeon and ferret, it occurs extensively. Other infrequently reported conjugations include serine conjugation of xanthurenic acid in rats excretion of quinaldic acid as quinaldylglycyltaurine and quinaldylglycylglycine in the urine of the cat, but not of the rat or rabbit and conversion of furfural to furylacrylie acid in the dog and rabbit, but not in the rat, hen, or human. The dog and... 

L-Cysteine is a precursor of the thioethanolamine portion of coenzyme A and of the taurine that conjugates with bile acids such as taurocholic acid (Chapter 26). 

The most active subcellular fraction for conjugation of bile salt CoA intermediates with taurine or glycine is microsomal (32). The system is strongly stimulated by the addition of a lysosome fraction, which may contain some peroxisome particles (33). Taurine and glycine are the only amino acids known to conjugate with bile acids in man, and the conjugation appears to be limited to the liver. In healthy adults, the usual glycine/taurine ratios are... 

The functional significance of decreases in plasma taurine is uncertain. As the only known bioch nical f mction of taurine is conjugation with bile acids (Encrantz and Sjovall, 1959)> measurement of taurine pools in liver and bile could be helpful in assessing the potential functional effects of a taurine-deficient diet. Measurement of the cerebral pool of taurine might also be helpful in assessing the availability of taurine for its putative function as a neurotrans-... 

Taurine was discovered in 1827 in ox hUe, where it is conjugated with the bile acids. It was later shown to be a major excretory product of the sulfur amino acids methionine and cysteine. Until about 1976, it was assumed that it was a metabolic end-product whose only function was the conjugation of bile acids. In the rat, taurine synthesis accounts for 70% to 85% of total cysteine catabolism. 

Conjugation of bile acids with taurine and glycine. 

V7. Vessey, D. A., The biochemical basis for the conjugation of bile acids with either glycine or taurine. Biochem. J. 174, 621-626 (1978). 

The formation of conjugates of taurine or glycine is induced by glucocorticoids, specifically dexamethasone [49]. In primary cultures of rat fetal liver dexamethasone increased and maintained taurine conjugation of cholate, chenodeoxycholate, and deoxycholate short-term cultures of adult rat hepatocytes maintained conjugation of bile acids with glycine and taurine [49]. Enzymatic activity was stimulated by low doses of ethynylestradiol [50], and has been verified in fetal liver [51]. 

Bile salts with a steroid structure appear to be confined to vertebrates (76). In some evolutionarily more primitive vertebrates, the major bile salts are sulfate esters of polyhydroxy C27- and C26-steroids and/or taurine-conjugated C27-steroid acids. In other primitive vertebrates, C24 bile acids, usually cholic acid and/or allocholic acid, or mixtures of primitive bile salts (bile alcohols and C27 bile acids) and modern bile salts (C24 bile acids) occur. Most of the work concerning the structure and occurrence of primitive bile salts has been carried out in the laboratories of G. A. D. Haslewood and T. Kazuno, and Haslewood and collaborators have accumu-... 

Hepatic bile acid production is also changed qualitatively. The conjugation of bile acids with glycine is significantly decreased in liver biopsies from cirrhotic patients (194). However, the ratio of glycine- to taurine-... 

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