i LIVING MATTEE 33 



(6) Amy-olytic enzymes or amylases, which split the poly- 

 saccharides (starch, etc.) into di- or mono-saccharides. To these 

 belong the various diastases of the animal and plant kingdom 

 (ptyalin, aniylopsin). The so-called invertases which split di- 

 saccharides into mono-saccharides are in close relation with these ; 

 e.g. maltase which splits maltose into two molecules of glucose ; 

 invertase, which splits saccharose into one molecule of fructose and 

 one of glucose ; lactase, which splits lactose into one molecule of 

 glucose and one of galactose. 



(c) Lipolytic enzymes or Upases, which split neutral fats into 

 their components, i.e. glycerin and fatty acids. To these belongs 

 the so-called steapsin of the pancreatic juice to which, according 

 to -the latest investigations, must be added another lipase, formed 

 by the gastric mucosa. 



The class of hydrolytic ferments further includes a number of 

 other ferments recently discovered in the tissues and organs of 

 animals and plants, such as arginase, which splits arginine into 

 urea and ornithine ; adenase and guanase, which split up adenine- 

 and guanine respectively into ammonia and hypoxanthine or 

 xanthine ; urease, which splits urea into ammonia, water, carbonic 

 acid, etc. 



A special position (which has been little noticed) is occupied 

 by the so-called coagulating enzymes, such as the rennin or 

 chyrnosin of the digestive tube, which forms casein from the 

 caseinogen of milk, and thrombin or thrombase, which determines 

 the clotting of blood by transforming fibrinogen into fibrin, as we 

 shall see in treating of blood plasma. 



The class of oxidising ferments contains all those ferments 

 which determine the disintegration of complex substances by 

 oxidising them, by a process highly similar to that which occurs in 

 inorganic nature in the various forms of combustion, e.g. of carbon, 

 which burns, combining with the oxygen of the air. 



These ferments, too, are analytic, i.e. they break down the 

 complex chemical compounds into simpler compounds, making 

 them richer in oxygen derived from the atmosphere or other 

 sources and thereby liberating a certain quantity of potential 

 chemical energy. Great importance is ascribed to these oxidising 

 ferments, as they are the agents of the various processes of oxida- 

 tion, which occur, as we shall frequently find, within the living 

 organism : and it has been possible, by modern methods of research, 

 to isolate a large number of enzymes belonging to this class from 

 animal and vegetable tissues. 



Direct oxidases (the name given to the oxidising ferments) 

 must be distinguished from the indirect, which are known as- 

 peroxidases. The former are capable of causing oxygen to 

 act directly; the latter can only oxidise in the presence of 

 peroxides (hydrogen peroxide). Oxidases give a blue reaction 

 VOL. i D 



