CHAPTER V. 



THE CLEAVAGE-PRODUCTS OF THE ALBUMINS. 



I. THE MONO-AMINO-ACIDS. 



THE mono-amino-acid derivatives of the albumins are glycocoll 

 (glycin), alanin, amino-isovalerianic acid, leucin, isoleucin, serin, 

 aspartic acid, glutaminic acid, phenyl-alanin, tyrosin, a-pyrrollidin 

 carbonic acid (prolin), tryptophan, oxy-pyrrollidin carbonic acid 

 (oxyprolin), and cystin. Of these, glycocoll, alanin, amino- 

 isovalerianic acid, leucin, and isoleucin are amino-derivatives of 

 monobasic acids of the formic series. They have neither marked 

 acid nor basic properties, but in a manner unite both. 



Glycocoll or glycin is amino-acetic acid : CH 2 (NH 2 ).COOH. 



Alanin is a-amino-propionic acid : CH 3 .CH(NH 2 ).COOH. 

 Having an asymmetric carbon atom, it is optically active (dextro- 

 rotatory). This is true of all the decomposition-products of albumin, 

 with the exception of glycocoll. 



The amino-valerianic acid which results on decomposition of 

 albumins is amino-isovalerianic acid : 



^ CH.CH(NH 3 ).COOH. 



It is dextrorotatory. 



Leucin is amino-isobutyl-acetic acid : 



j>CH.CH 2 .CH(NH 2 ).COOH ; 



the usual product obtained on hydrolysis of albumins is Isevorota- 

 tory. 



Isoleucin corresponds to an a-amino-methyl-ethyl-propionic acid : 



>CH.CH(NH,).COOH. 



Serin is an a-amino-/?-oxypropionic acid. It is thus closely related to 

 alanin and represented by the formula : CH 2 (OH).CH(NH 2 ).COOH. 

 Only the racemic form has thus far been obtained. 



Aspartic acid and glutaminic acid are dibasic acids of the oxalic 

 series. Both have markedly acid properties. 



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