Birds, amino acid conjugation

The major substrates for amino acid conjugation are benzoic acid and related aromatic carboxylic acids such as phenylacetic acid, phenoxyacetic acid, cinnamic acid, etc. (21). In humans, the major amino acid utilized in the conjugation is glycine however, glutamine and taurine can also be cofactors. In birds, the major amino acid utilized is ornithine. 

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. 

The main amino acids used to form the conjugates are glycine, glutamine, ornithine (birds), alanine (hamsters and mice), arginine and taurine. 

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. ... 

The dog does, however, acetylate the Nl, sulfonamido group of sulfanilamide (chap. 4, Fig. 68), and also acetylates aliphatic amino groups. The guinea pig is unable to acetylate aliphatic amino groups such as that in cysteine. Consequently, it excretes cysteine rather than N-acetylcysteine conjugates or mercapturic acids. Birds, some amphibia, and insects are also able to acetylate aromatic amines, but reptiles do not use this reaction. 

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