Practical physiological chemistry; a book designed for use in courses in practical physiological chemistry in schools of medicine and of science . e of the amino acids. It is possible that thedibasic acids, aspartic and glutamic, furnish most of these carboxylgroups. This is indicated by the more or less close relationship whichexists between the amount of ammonia and that of the dibasic acidswhich the several proteins yield upon decomposition. The eliminationof the ammonia from proteins under the action of acids and alkaUs isvery similar to that from amides like asparagine. Glycocoll, CH2-(XH
Practical physiological chemistry; a book designed for use in courses in practical physiological chemistry in schools of medicine and of science . e of the amino acids. It is possible that thedibasic acids, aspartic and glutamic, furnish most of these carboxylgroups. This is indicated by the more or less close relationship whichexists between the amount of ammonia and that of the dibasic acidswhich the several proteins yield upon decomposition. The eliminationof the ammonia from proteins under the action of acids and alkaUs isvery similar to that from amides like asparagine. Glycocoll, CH2-(XH2)-COOH.—Glycocoll, or amino acetic acid, is 72 PHYSIOLOGICAL CHEMISTRY the simplest of the amino acids which occurs as a protein decompositionproduct^ and has the following formula: NH2H—C—COOH. H Glycocoll, as the formula shows, contains no asymmetric carbon atom,and is the only amino acid yielded by protein decomposition which isoptically inactive. Glycocoll and leucine were among the first decom-position products of proteins to be discovered. Upon administeringbenzoic acid to man or lower animals the output of hippuric acid in the. Fig. 21.—^Glycocoll Ester Hydrochloride. urine is greatly increased, thus showing a synthesis of benzoic acid andglycocoll in the organism (see page 585, Chapter XXVII). Glycocoll,ingested in small amount, is excreted in the urine as urea, whereas ifadministered in excess it appears in part unchanged in the urine. It isusually separated from the mixture of protein decomposition productsas the hydrochloride of the ester. The crystalHne form of this com-pound is shown in Fig. 21. Alanine, CH3-CH(NH2)^Alanine is a-amino-propionic acid,and as such it may be represented structurally as follows: H NH2H—C—C— H ^ Amino formic acid (carbamic acid), NH2COOH, is the simplest amino acid. PROTEINS 73 Obtained from protein substances, alanine is dextro-rotatory, is verysoluble in water, and possesses a sweet taste. Tyrosine, phenylal
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