Abstract
It appears to be a specific function of several of the amino acids to combine with certain substances which the body is unable to oxidize. When benzoic acid and the numerous aromatic substances which are converted into benzoic acid in the body are ingested by man and certain other animals they are eliminated in the urine almost quantitatively as hippuric acid. Phenylacetic acid is voided in the urine of the dog and of the rabbit conjugated with glycocoll as phenaceturic acid 1 while in man it combines with glutamine and appears in the urine as phenylacetylglutamine. 2 The following also belong to the list of substances which undergo conjugation with glycocoll in passing through the body: furfurol 3 which in part is first oxidized to pyromucic acid and excreted as pyromucuric acid and in part combines with acetic acid and is eliminated as furfuracryluric acid, α-methylthiophene 4 which is oxidized to α-thiophenic acid and appears in the urine as thiophenuric acid, and α-methyl pyridin (α-picolin) 5 which after oxidation to α-pyridin carboxylic acid passes into the urine as α-pyridinuric acid. The rôle which in animals is given to glycocoll is taken in birds by ornithin. 6 Ingestion of benzoic acid by chickens leads to the appearance of ornithuric acid and similarly, pyromucic acid is conjugated with ornithin to give pyromucinornithuric acid. In certain instances the part of the conjugating amino acid is taken by cystein 7 and by taurin. Halogen combinations of benzol and naphthalin are linked in the body with cystein and this substance, after acetylation of the amino group, appears in the urine combined with glucuronic acid. In the bile of most animals both glycocoll and taurin are found in combination with cholic acid although in the bile of the dog and of the sheep taurocholic acid appears to be the only bile salt present. 1
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