458 ENZYMES 



becoming smaller and smaller. Finally, at the end of the 

 secretory activity, the protoplasm of the gland-cells breaks 

 down, and the products of its disintegration disapppear from 

 view. 



It may be remarked that in the dried condition enzymes 

 may retain their characteristic power for a considerable time ; 

 thus White * found that the ferments — diastase, protease, and 

 ereptase — of the resting fruits of wheat and barley retained 

 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 exposure to a temperature of 130° for one hour, 

 however, did destroy 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. f 



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,t 

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

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

 nuclease, amidase, lipase, emulsin, amylase, inulase, raflfinase, 

 sucrase, maltase, lactase, catalase, and phytase, considers, 

 from the data at hand, that these enzymes are formed regard- 

 less of the chemical nature of the substrate. 



Observations such as these open up many questions relating 



* White : " Proc. Roy. Soc. Lond.," B., 1909, 81, 417. 

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

 J Went : " Jahrb. Wiss. Bot.," 1901, 36, 611 ; see also Pringsheim 

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

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



