EFFECTS OF RADIATION ON ENZYMES 1155 



diastase proved to be more easily inactivated (67/) by ultra-violet radia- 

 tion than the malt diastase preparations employed, and in the former 

 case the addition of certain salts, especially salts of iodine, decreased 

 the amount of injury. Pancreatic diastase and ptyalin were protected 

 by KI, but not malt diastase (67e). 



With malt diastase the protective action of NaCl was least at pH 

 6.64 (67e). Small quantities of other salts showed greater protective 

 action than larger amounts. In general (67^) there is a protective action 

 of the chlorides of K, Ca, Mg, Li, and Pb, the order of the protection 

 varying with the different diastases and also with the concentration of 

 the salts and of the enzyme solutions. Usually the K salts offered the 

 least protection, and Ca salts the greatest. 



It was also found (67m) that certain sensitizers (eosin, sodium 

 dichloroanthracene disulfonate, and sodium anthraquinone disulfonate) 

 as well as certain impurities present in the enzyme solutions exert a 

 protective action on the enzyme. The greatest inactivation occurred 

 at the optimum pH for digestion, with or without the addition of the 

 sensitizers. The lecithase and phosphatase in a Taka diastase prepara- 

 tion were irradiated with the mercury-vapor arc (67o), and at pH 6.6 

 phosphatase was much more seriously inactivated by ultra-violet light 

 than was lecithase. The course of inactivation followed the law for a 

 reaction of the first order. Greater inactivation of Taka diastase by 

 ultra-violet light occurs at pH 5.91-5.97 (67n), which also is its activity 

 optimum. Heat resistance is greatest at alkaline reactions. Ultra- 

 violet combined with heat (45° to 50°C.) is most powerful at pH 4.83 to 

 4.89. Heat and ultra-violet destructions are thus assumed to have 

 different mechanisms. 



Terroine and Bonnet (88) found that diastase of the pancreatic juice 

 of a dog and that of the gastroenteric juice of a snail {Helix pomatia) are 

 more sensitive to the destructive action of ultra-violet rays when they 

 are exposed in the presence of NaCl than when exposed in their inactive 

 forms (obtained by prolonged dialysis). The variations of sensitivity 

 to ultra-violet radiation and heat rays of the active and inactive diastases 

 were neither general nor regular. 



Thompson and Hussey (89) irradiated a diastase solution prepared 

 from pancreatin in 0.85 per cent saline. The enzyme was irradiated in a 

 flat bottomed cylindrical quartz tube placed vertically above a quartz 

 window, and in the bottom of a thermo-regulated water bath at 10°C. 

 The quartz-mercury lamp employed was 19 cm. below the quartz window. 

 The enzyme solution was stirred during the experiment, and a control 

 in a light-screened container was held in the same bath. Apparently no 

 attempt was made to measure light intensity or quality. The diastase 

 in solution was inactivated by the radiations, and the reaction course was 

 that of a monomolecular reaction. The reaction was followed to a 



