Mammals amino acid conjugations

Therefore, a similar pathway appears to operate in certain mammals. When S-(PCP)ThioAcetate was introduced into peanut plants, pentachlorothioanlsole was not formed. However, other metabolites were detected, possibly glucose and amino acid conjugates similar to those reported for 2,4-D (17). 

Amino Acid Conjugation. In the second type of acylation reaction, exogenous carboxylic acids are activated to form S-CoA derivative in a reaction involving ATP and CoA. These CoA derivatives then acylate the amino group of a variety of amino acids. Glycine and glutamate appear to be the most common acceptor of amino acids in mammals in other organisms, other amino acids are involved. These include ornithine in reptiles and birds and taurine in fish. 

Amino acid conjugation has been reported to occur with glycine, glutamine, arginine, and taurine in mammals and certain primates. In other organisms, different amino acid acceptors are utilized in peptide conjugation. Ornithine is utilized by... 

Xenobiotic carboxylic acids can be excreted as amino acid conjugates, where the COOH grot ) forms an amide bond with the -NHg group of an amino acid. In mammals, the aminn acid most commonly used for conjugation is glycine. This pathway has been studied in vitro and In vivo in several fish species and a marine Invertebrate. 

Several other amino acids arc involved in the conjugation ofcarbo.xylic acids, but these reactions occur only occasionally and appear to be highly substrate and species depen-denl. " Ornithine (in birds), aspartic acid and serine (in rals), alanine (in mouse and hamster), taurine iH NCH CH2SO]H) (in mammals and pigeon.s), and histidine (in African bats) are among these amino acids. ... 

When heme proteins are degraded in mammals, the polypeptides are hydrolyzed to amino acids while the heme groups are freed of their iron, which is salvaged, and are converted to bilirubin. After transport to the liver, bilirubin is coupled to glucuronic acid and the conjugated bilirubin is excreted into bile as the principal bile pigment. When increased production or decreased excretion of bilirubin causes its plasma concentration to exceed 0.1-1.0 mg/dL (2-17 /rmol/L), it diifuses into tissues and... 

In mammals, GSH S-conjugates, the metabolites of GSH S-transferase catalyzed reactions, are subject to further metabolism by a series of three enzyme-catalyzed reactions to form the corresponding N-acetylcysteine derivative or mercapturic acid, which is excreted in urine (3). The same group of three enzymes are also involved in recycling of GSH and in amino acid transport. The first step is catalyzed by y-glutamyltransferase (EC 2.3.2.2), an enzyme localized on the outer surface of most cells. This enzyme has been detected in A. suum (57), S. mansoni (58) and T. cruzi epimastigotes (59). However, there is no evidence that parasites metabolize GSH... 

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