1912.] Studies on the Reductase of Liver and Kidney. 493 



shaken. At the end of this time 5 c.c. were pipetted off from each tube,, 

 diluted with distilled water, and rapidly filtered from protein material. The 

 clear, light brown filtrates were then decolorised by shaking with powdered 

 animal charcoal, which was subsequently removed by filtration. The colour- 

 less filtrates were finally tested for nitrite with Griess' sulphanilic acid 

 reagent, and the amount of nitrite determined colorimetrically. The follow- 

 ing are the results obtained : 



The nitrite contained in 5 c.c. of the active liquid was found to correspond 

 to 7*65 c.c. of the standard* nitrite solution. Therefore the nitrite contained 

 in the whole solution was equivalent to 1*47186 mgrm. The nitrite contained 

 in the total volume of boiled liquid was less than 0*04 mgrm. 



Another experiment similar in every respect to the above, except that the 

 20 c.c. of the sodium nitrate solution added to each tube contained 2*5 grm. of 

 the salt, gave the following results : 



The nitrite contained in 5 c.c. of the active liquid was found to correspond 

 to 5*90 c.c. of the standard nitrite solution. Therefore the nitrite contained 

 in the whole active solution was equivalent to 1*13516 mgrm. The nitrite 

 contained in the total volume of boiled liquid was less than 0*03 mgrm. 



From these experiments it will be observed that the amount of reduction 

 brought about by the active press juice is not inconsiderable, while, on the 

 other hand, boiled press juice reduces little or no nitrate. This behaviour 

 affords additional support to the enzymic character of tissue reduction. 



As it seemed probable that many important and interesting results; 

 regarding the nature of reductase might be obtained by studying the velocity 

 of reduction, we attempted to follow the change in concentration of the 

 soluble Prussian blue solutions by means of electrical conductivity measure- 

 ments. This method, however, had to be abandoned owing to the extremely 

 small changes in conductivity that were found to occur in the reactions 

 investigated. 



Owing to the ease and accuracy with which measurements on the reduction 

 of nitrates can be carried out colorimetrically, we intend, in the immediate 

 future, to employ this reaction for the quantitative study of reductase. 



IV. Summary of Conclusions. 



1. The existence of a catalytic enzyme in the mammalian liver is fully 

 confirmed. The decomposition of hydrogen peroxide is effected by this enzyme 

 and is not due to the presence of proteins or other organic matter in the press 

 juice. "We intend to study further the behaviour of this hepatic catalase. 



2. We find the existence of a reducing endo-enzyme (reductase) confirmed. 

 * 1 c.c. of the standard solution employed contained 0*02405 mgrm. of sodium nitrite. 



