OCCURRENCE 347 



their activity after twenty years, by which time the power of 

 germination is lost. Also, that the subjection of the dry grains 

 to certain extremes of temperature did not destroy the enzymes. 

 Thus the heating of dry oats to 100 C. for four and a half hours 

 was without effect in the destruction of the enzymes ; an ex- 

 posure to a temperature of 130 for one hour, however, did de- 

 stroy the ferments. On the other hand, a temperature of 

 200 C. did not destroy the dry diastase of barley. 



The number of enzymes which a plant may contain is sur- 

 prising ; thus in Beta vulgaris, the leaves contain invertase, 

 diastase, and maltase, the stem possesses invertase, diastase, 

 inulase and emulsin, and the root diastase, maltase, inulase, 

 and emulsin, but not invertase.* 



The moulds the digestive activities of which are, to a 

 great extent, extra-cellular also exhibit marked powers of 

 secreting different enzymes. Thus Monilia sitophila may form 

 maltoglucase, trehalase, raffinase, invertase, cytase, diastase, 

 lipase, tyrosinase, and trypsin. These, according to Went,f 

 are secreted according to the nature of the food ; Dox,J how- 

 ever, who has demonstrated the presence in moulds of protease, 

 nuclease, amidase, lipase, emulsin, amylase, inulase, raffinase, 

 sucrase, maltase, lactase, histozyme, catalase and phytase, 

 considers, frorp the data at hand, that these enzymes are formed 

 regardless of the chemical nature of the substrate. 



Observations such as these open up many questions relat- 

 ing to the nature of enzymes ; are all these different ferments 

 really specific, or are there only a few enzyme-nuclei which, 

 before they can attack any particular substance, have to have 

 attached to them certain molecular complexes according to 

 the nature of the substrate ? 



There may, in certain cases, be made out a curious associa- 

 tion of different enzymes. Thus Vines found that when a 

 tissue gave the guaiacum reaction, with or without the addition 

 of peroxide, that same tissue also exhibited proteolytic activity 

 and vice versa. Thus in the fruit of the orange, neither the 

 juice nor the pulp gives the guaiacum reaction, whilst, on the 



* Robertson, Irvine, and Dobson : " Biochem. Journ.," 1909, 4, 258. 

 fWent: "Jahrb. Wiss. Bot.," 1901, 36, 611 ; see also Pringsheim and 

 Zempter : " Zeit. physiol. Chem., " 1909, 62, 367. 

 Dox: " Plant World," 1912, 15, 40. 

 Vines : " Ann. Bot," 1903, 17, 257. 



