THE ACTIVITY OF ENZYMES AND 

 COENZYMES IN IRRADIATED TISSUES 



Antoinette Pirie 



Nuffield Laboratory of Ophthalmology, University of Oxford 



The biochemical effects of radiation have been recently 

 reviewed by Ord and Stocken (1953), DuBois and Petersen 

 (1954), Errera (1955) and by Bacq and Alexander (1955) and 

 these valuable reviews form the basis from which any survey 

 of this jungle of a subject must be made. They make a general 

 survey of the jungle unnecessary and I propose to define the 

 problem as best I can and then to describe in some detail 

 those pieces of experimental work which provide evidence for 

 an initial effect of radiation on enzymes in the cell. The 

 effect of radiation on DNA, RNA, protein and phosphorus 

 metabolism is being considered by other speakers and will 

 not be touched upon. 



If we are looking for an effect of radiation on cell enzymes, 

 what characteristics should we demand? A change in enzyme 

 activity found after radiation of the whole animal could be a 

 direct or indirect effect, i.e. reaction with the ionizing radiation 

 or particle itself or with the radicals formed in the medium. 

 It could also be a secondary effect resulting from structural or 

 chemical changes in other molecules which repercuss on the 

 activity of the particular enzyme we are studying. It seems 

 probable that such secondary effects on enzymes will become 

 more marked with time unless recovery sets in. Both direct 

 and indirect effects will be instantaneous and may be detect- 

 able as soon as it is possible to test ; but they may or may not 

 be maximal at this time. An enzyme, slightly damaged by 

 direct or indirect action, may continue to deca}^ Thus, for 

 example, Anderson (1954) found that pepsin, and McDonald . 

 (1954) found that trypsin gradually lose further activity dur- 



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