Bile acids peptide bond

To deconjugate bile acids for further analysis, particularly by gas-liquid chromatography, different methods are required for the hydrolysis of the peptide bonds in glycine and taurine conjugates than for hydrolysis of the ester sulfate and glucuronide bonds. Glycine and taurine may be removed by either alkaline or enzymatic hydrolysis (Rll). Alkaline hydrolysis is often... 

The ability to hydrolyze the peptide bond in conjugated bile acids (Fig. 1) is widely distributed among intestinal bacteria. Conjugated bile acid hydrolase (CBH) (EC 3.5) activity has been detected in members of the genera Bacteroides, Bifidobacterium, Fusobacterium, Clostridium, Lactobacillus, Peptostreptococcus and Streptococcus [13-17]. However, there is considerable variation in occurrence of this enzymatic activity among species and strains. 

The terminal step in the biosynthesis of bile acids from cholesterol is represented by the enzymatic synthesis of water-soluble bile acid conjugates of taurine and/or glycine through a peptide bond, as shown in Fig. 1. 

In Section II, we have discussed the enzymatic synthesis of the peptide bond of bile acid conjugates by mammalian liver. The further metabolism of... 

Bile adds components of bile which serve as emuldfying agents. They are steroid carboxylic adds linked to taurine or glycine by a peptide bond. According to the constituent amino add, they are called glycocholic or taurocholic acids. Ihe former predominate in human and bovine bile, the latter in canine bile. B. a. are characteristic of mammals in lower vertebrates the same function is performed by Bile alcohols (see). In mammals, the pattern of B.a. is often spedfic for the spedes. 

Primary bile acids generally exist in bile in the form of conjugates with glycine or taurine through a peptide bond. These water-soluble conjugates, by virtue of their surface active properties, solubilize lipophilic substances in the gut, forming micelles in the process. The structures of two such compounds, glycocholic (XIII) and taurocholic (XIV) acids, are shown in Fig. 8. 

The rate of hydrolysis may vary with the bile acid structure. The hindered nature of the peptide bond in the taurine-conjugated 3 ,7a, l2a-trihydroxy-5 3-cholestanoic acid may explain why this conjugate is more resistant to saponification than C24 acids (59). 

All bile acids are secreted in the bile exclusively as glycine and taurine conjugates, the glyco- and taurocholic acids (Haslewood 1955, Ahrens et al. 1952). Amino acid and bile acid are linked by a peptide bond ... 

Since the RIA for bile acids was described in 1973 by Simij oggs et al., several different procedures have been reported in the literature, the main characteristics of which are summarized in Table 1. All methods utilize polyclonal antibodies produced in rabbits immunized with a bile acid coupled to a protein. The carrier protein generally bovine serum albumin, has been covalently linked by a peptide bond on a carboxy group. 

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