PRODUCTS OF HYDROLYSIS OF PROTEIN'S. 23 



taken to produce a given change on a given quantity of hydro- 

 lyte is inversely proportional to the quantity of hydrolyst. Each 

 hydrolyst has a certain optimum temperature at which it acts 

 most rapidly, the action being diminished at both higher and 

 lower temperatures. Certain substances — e.y., acids — affect the 

 rate of hydrolysis by enzymes ; their influence, however, follows 

 laws which are not fully known. This may be perhaps due to 

 the hydrolysing effects of the acid combined with those of other 

 hydrolysts taking a course influenced by both of them. 



Fischer separates the amino-acids obtained by long boiling with 

 acids by esterifying, crystallising out the glycine ester, and dis- 

 tilling the others in vacuo, and extracting with ether. Fischer 

 and Bergell also convert the amino-acids into their /?-naphthalene 

 sulphonates, which are very slightly soluble. These methods 

 involve, howevei-, some loss, but they give a rough estimate of 

 the proportions of the amino-acids. 



A large number of amino-acids have been separated from the 

 products of continued hydrolysis of proteins ; these are — 



A. Mono-amino-mono-carboxylic acids. 

 Amico-acetio acid, or glycine. 

 Amino-propionic acitl, or alanine. 

 Amico-butyrio acid. 



Amino- valeric acid or valine. 

 Iso-bulyl-amiiio-acctic acid, or leucine. 



B. Hydroxy-mono-amino-mono-carboxylic acids. 

 Hydroxy-amino-propionic acid, or serini'. 

 Tetra-hydroxy-amiuo-caproic acid. 



C. Mono-amino-di-carboxylic acids. 

 Amino-succinic acid, or aspartic acid. 

 Amino-glutaric acid, or glutamic acid. 



D. Hydroxyraono-amino-di-carboxylic acids. 

 Hydroxy-amino-succinic acid. 

 Hydroxy-amino-subcrio acid. 



E. Di-amino-mono-carboxylic acids. 

 (i-t(-diamino-propionic acid. 

 «-e.diamino-caproic acid, or lysine, 

 a-o-diamino-valerio acid, or ornithine. 



F. Substituted-mono-amino-mono-carboxylic acids, 

 a-amino-o-guanidine- valeric acid, or argininc. 

 a-amino-/J-iininazolyl propionic acid, or liistidine. 



The constitution of arginine and histidine is as below : — 



Argiiiiiu'. Histidine. 



CH,— NH CH— X 



I " >C— XH, II >CH. 



CH., XH' ■ C— XH 



i " I 



CH, CH. 



I " I 



CH— XH, CH..— XH. 



I ' I 



COOH COOH. 



