AMINO-ACIDS, PROTEINS, UREA AND URIC ACID 85 



acid it hydrolyzes, forming benzoic acid and amino-acetic acid. 

 The free amino-acetic acid then with the HCl yields the hydro- 

 chloric acid salt. 



CeHs-CO 



+ 

 HO 



NH-CH2-COOH 



-> C6H5-COOH+(NH2)CH2-COOH 



H Benzoic acid Amino-acetic acid 



Hippuric acid+H20 



Hippuric acid is important as a product of animal metabolism 

 and will be considered again under that subject. Amino- 

 acetic acid commonly goes by another name, especially in con- 

 nection with its physiological relationships. It is known as 

 glycine; the prefix, glyc, of this name indicates its sweet taste, 

 and the termination, ine, its amine nature. 



Alanine, a-amino-propionic acid: CH3— CH(NH2) — COOH 



This compound, the next higher homologous amino-acid, is 

 the amino analogue of lactic acid. 



Lactic acid, a-hydroxy-propionic acid: CH3— CH(OH) — COOH 

 Alanine, a-amino-propionic acid : CH3 — CH(NH2) — COOH 



Like lactic acid, it contains an asymmetric carbon atom (under- 

 lined) and possesses optical activity, being known in its dextro, 

 levo and inactive forms. The compound is similar to glycine 

 . in its properties, being a solid crystalline compound forming 

 salts with both bases and acids, and also derivatives of the acid 

 amide type as discussed under glycine. 



Higher Amino-acids 



A few other amino-acids will be mentioned, simply giving 

 their constitutional formulas, in order that they may be referred 

 to later. 



Valine, a-amino-/3-methyl-butyric acid : 



CH3 - CH - CHCNHo) - COOH 



CH. 



