XXXVII 



THE EFFECTS OF RADIATION ON ENZYMES 

 Harold A. Schomer 



Department of Botany, University of Wisconsin 



The study of the relation of light to enzymes may be divided into two 

 parts: (o) the use of light in the study of the structure of enzymes, mainly 

 their absorption spectra, and (6) the possible effects of the absorbed 

 radiation on the enzymes. Since the greatest progress in the purification 

 of enzymes and in the perfection of physical apparatus in the field of 

 radiation has been made in comparatively recent years, early work on 

 irradiation of enzymes was necessarily rather crude and qualitative. 



In 1879 Downes and Blunt (19) found that invertase ("zymase" from 

 a fragment of yeast macerated in water and filtered) was inactivated 

 by the full solar spectrum in the presence of oxygen. They concluded 

 that the chief injury was due to the blue-violet portion, and that the 

 inactivation was an oxidation reaction. Fermi and Pernossi (23) studied 

 the effect of sunlight and temperature, together with various acids and 

 salts, on various enzymes, the sources of which are not described. Pepsin 

 and trypsin were found to be inactivated by long exposure (10 days) to 

 sunlight. It was also reported that greater inactivation by light occurred 

 at higher temperatures (54° to 56°C.), than at lower temperatures (37°C.). 

 When exposed in the dry condition, these enzymes retained their activity 

 over long periods of time (3 months). Similar results were obtained 

 with ptyalin, diastase, and emulsin in the dry state, and in the presence 

 of chloroform, ether, amyl alcohol, or benzol. Bacteria, exposed to 

 sunlight, lost considerable of their proteolytic activity. 



Green (30) made extensive studies on the action of sunlight and light 

 from an electric arc upon malt diastase solution, diastase in leaf tissue, 

 and upon human saliva. Over a 24-hr. period, bright sunlight had no 

 effect, while diffused light was found to increase slightly diastatic activity. 

 After an exposure of 10 days the diastatic activity decreased 93 per cent. 

 The various diastase solutions were also exposed to an electric arc of 

 2000 candle power at a distance of 2 ft. for 10-, 12-, and 24-hr. periods. 

 Exposures were made in open Petri dishes, the enzyme solutions being 

 mixed to a gel with agar, then disposed in quartz vessels and in glass 

 vessels. The entire spectrum was found to exert an attenuating influence 

 on the diastatic activity; visible and infra-red rays (passed through glass) 



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