Diastase and its Biological Significance. 



27 



The infra-red, red, orange, and blue regions gave increases of 108, 

 53"5, -±'75, and 20*8 per cent. ; the green a diminution of 15*7 per 

 •cent. The violet gave also a marked diminution, but it was not 

 measured, as no satisfactory screen, allowing only the violet rays to 

 pass, could be devised. The paper is illustrated by a curve showing 

 these effects. 



The effects of the illumination were found to be progressive, the 

 increase or diminution of the diastase continuing after the solutions 

 were removed from the access of the several rays. 



The deleterious rays were found to be absorbed by the solution, 

 the absorption being effected partly by the diastase itself, whether 

 boiled or unboiled, and partly by the proteids present in the extracts. 

 After removal of the latter by boiling and filtration, the solution was 

 still opaque to the rays. 



The screening influence of proteids was examined separately, by 

 .adding small quantities of egg-albumin to the extracts. The latter 

 was found to be protective, the degree of protection being however, 

 only roughly proportional to the amount of albumin present. 



The colouring matter of the barley grain was also ascertained to 

 act as a screen for the deleterious rays. 



The living leaf was also examined by the same method as the 

 extracts, and the diastase in it was found to undergo a similar 

 •destruction under the influence of the light. 



It was found impossible to investigate the possible protective 

 influence of chlorophyll in the leaf, as all the solvents of the latter 

 proved to be opaque to the ultra-violet rays. They confirmed, how- 

 •ever, the view that the violet rays, and possibly the green, have a 

 destructive effect upon the enzyme. 



The experiments lead to the conclusion that there exists in the leaf 

 and in the various extracts examined a certain amount of zymogen 

 which is converted by the infra-red and the red, orange, and blue 

 rays into active diastase. This conclusion is supported by experi- 

 ments, detailed in the paper, upon the effect of keeping the solutions 

 for several days at a temperature of 38° 0. A curve of the effect of 

 this exposure is given in the paper. 



The violet and ultra-violet mys, on the other hand, cause a 

 •destruction of the diastase, or at least such a change in the configura- 

 tion of its molecule that it is unable to effect the hydrolysis of starch. 



Three other conclusions of some importance have resulted from the 

 •experiments : — 



1. That the enzyme is not located in the chlorophyll grain, but in 

 the protoplasm of the cell. 



2. That the suggestion of Pick* and Johowf that the red colour- 



* ' Bot. Central.,' vol. 16, pp. 9—12. 

 f ' Pringsheim's Jahrb.,' vol. 15, p. 299. 



