[HARRIS] A REDUCING ENDO-ENZYME 133 



2. — The behaviour of the juice in regard to temperature is the next 

 point indicating the presence of an enzyme. 



Its optimum is between 42°C and 46°C. Thus Herter found re- 

 duction processes were accelerated in the experimentally induced fever 

 of hog-cholera. As the temperature falls, the rate of reduction is dim- 

 inished, until at zero reduction is entirely inhibited. But at a temp- 

 erature as low as minus 14°C, the reducing power is not destroyed; it 

 is merely kept in check. 



I have kept under observation a mixture of absolutely fresh liver- 

 juice and Prussian blue, surrounded by a freezing mixture for 24 hours, 

 without noticing the least degree of fading of the deep blue colour. On 

 removing the tube from the freezing mixture, the colour was completely 

 discharged by the time the juice had reached room-temperature 17°C. 



Herter found in the intact animal that " the power of reduction was 

 much diminished by cold". 



A typical experiment may be quoted in connection with tempera- 

 tures. 



Three water-baths were brought to (a) between 40° and 41°C; (b) 

 between 42°C and 43°C, and (c) between 44° and 4o°C respectively. In 

 each bath a tube was placed containing 3 c.c. of raw hepatic juice shaken 

 up with 20 c.c. of Prussian blue all under toluene. In 6 hours the tube 

 in (a) was green, that in (b) was green-white, the one in (c) was quite 

 white ; twenty four hours later the tube in (b) was white. 



The behaviour of tissue juice is compatible with its active con- 

 stituent being an enzyme. 



3. As judged hy the Pozzi-Escot test, a reducing ferment is present 

 in certain tissues, for pieces of tissue, but better their juices, decompose 

 H2O2 without affecting a mixture of guaiacum and HgOj. 



That press-juice, for instance of liver, is more active than pieces 

 of liver is in accordance with the findings of other workers on ferments. 

 J.J. R. MacLeod -" noticed this in the case of glycogenase, an undoubted 

 endo-enzyme. 



4. The reducing action is accelerated or augmented by the pres- 

 ence of alkaline salts of the tissues, which behave as adjuvants. Pro- 

 fessor Irvine and I" concluded that reductase acted after the manner 

 of pyrogallol, an organic reducer, in an alkaline medium. 



5. In my recent work^^ on the action of protoplasmic poisons on 

 reductase, I found that the acidity (concentration of H ions) was a 

 more profound inhi])itant of the reducing power than was toxicity. 

 Concentration of H ions is well known as an inhibitant of the activity 

 of certain enzymes, to this reductase would not form any exception. 



The fact that reductase is not inactivated by certain virulent 

 protoplasmic poisons— chloroform, sodium fluoride, nitrobenzene, form- 



