22 CONSTITUENTS OF MILK 



reaction, and are injuriously influenced by toxins and various 

 salts. As they have never been isolated in a pure condition, 

 comparatively Uttle is known as to their composition and it is 

 by their properties rather than differences in composition that 

 enzymes are recognised. 



Amongst the various enzymes that have been discovered 

 in milk are amylase, galactase, hpase, lactokinase, peroxidase, 

 reductase, and catalase. 



Amylase. B^champ^^^ in 1883, prepared an amylase from 

 human milk that converted soluble starch into sugar as readily 

 as amylases from other sources. The presence of amylase in 

 cows' milk has been denied by Moro, der Velde, Landtsheer, 

 and Kastle and affirmed by Zaitschick, Koning, Seligman, 

 Jensen, and others. The author has invariably found amylase 

 to be present, although only in minute quantities. 



Galactase. This protease was first found in milk by Bab- 

 cock and Russell in 1897 ^s. They found that fresh centrifuge 

 slime showed proteolytic properties even when aU bacterial 

 activity was checked by the presence of antiseptics. Wender ^9 

 has shown that the galactase prepared from centrifugal slimes 

 is not a pure enzjnue but a mixture of galactase with peroxidases 

 and catalase. The presence of catalase in milk has, however, 

 been confirmed by von Freudenreich, Jensen, Spolverini, and 

 others. The action of galactase on proteids is very similar 

 to that of trypsin, proteoses and peptones being the inter- 

 mediate, and amino acids the final products. 



Lactokinase, a kinase similar to enterokinase, and a fibrin 

 ferment have also been found in minute quantities. 



Lipase, the enzyme capable of hydrolysing glycerides of 

 fatty acids such as monobutyrin, was found in milk by Marfan 

 and Gillet ^°. Cows' milk was found to have a lipolytic activity 

 of 6-8 on Hanriot's scale as against 20-30 for human milk. 



Salolase. That human and asses' mOk have the property 

 of hydrolysing phenyl salicylate (salol) was observed by Nob6- 

 court and Merklen.^i The existence of this ferment in milk 

 was disputed by D^smouliSrs and also by Mule and Willem, 



