62 SCIENCE PROGRESS 



which the activity of an enzyme varies with fluctuations ol 

 the temperature. The behaviour of reductase is wholly in 

 accordance with that of undoubted enzymes ; there is inhi- 

 bition but not destruction below and at o° C. As the temperature 

 rises there is greater and greater velocity of action, until the 

 destructive effects of heat begin to make themselves felt. That 

 is to say, there is an optimum and there is a destruction 

 temperature. 



3. The temperature coefficient of, approximately, 2 between 

 10 and 40 C. is in line with known enzymic action. 



4. This is also true of the logarithmic nature of the decay in 

 the activity of the enzyme. 



5. The deterioration with age of reductase in a moist medium 

 also conforms to the behaviour of other enzymes. It withstands 

 complete desiccation badly. 



6. The fact that poisons for catalysts similarly affect the 

 actively reducing substance in press-juice is in favour of that 

 substance also being an enzyme. 



7. The criterion of reversibility is one which is difficult to 

 apply to reductase. Stated baldly, the ferment does not induce 

 any reversed action in the direction of oxidation. Press-juices 

 reduce materials once for all, and no oxidation in virtue of the 

 presence of reducing agents is possible. Oxyhemoglobin once 

 reduced is not reoxidised. But since oxidases are always present 

 acting simultaneously with reductases, the chemical complex 

 oxidase-reductase is functionally equivalent to a reversible 

 ferment. In this connection one should remember that the 

 Cannizzaro reaction — simultaneous oxidation and reduction — 

 has actually been obtained when certain aldehydes were digested 

 with liver tissue, thus — 



2R.CHO + H 2 = R.CH 2 .OH + R.CO.OH 



where one molecule of the aldehyde is oxidised to the acid 

 and the other reduced to the alcohol. Parnas has in fact sug- 

 gested the term " aldehydemutase" for the hypothetical enzyme 

 concerned. 



The object of tissue respiration as distinct from tissue nutri- 

 tion may be said to be twofold : to produce heat and to prepare 

 katabolites for excretion. Thus carbohydrates are oxidised to 

 yield carbon dioxide and water as end-products, although exactly 

 how is not even yet thoroughly understood. As aldehydes 



