[HARRIS] A REDUCING ENDO-ENZYME 135 



Vernon has shown, there are oxidases in the liver which must of necessity 

 work in the direction opposite to that taken by the reductase. 



Hence when we obtain a less distinct reduction than we expect, we 

 have to remember that the oxidase may have been active. We have, in 

 fact, the converse of the difficulty to which Dr. Vernon" alluded when 

 investigating " The quantitative estimation of the indophenol oxidase of 

 animal tissues", he wrote — "The unavoidable presence of reducing sub- 

 stances, some of which are possibly enzymes or "reductases", acts in 

 direct antagonism to the oxidases, and under certain conditions entirely 

 overpowers them. Hence the absence of an oxidising action cannot be 

 held to indicate the absence of oxidase, unless the conditions are so chos- 

 en to give the oxidase the best possible chance of exerting its activity. " 



At an early stage I had noticed that in a tube in which the Prussian 

 blue had been completely reduced to the leuco state, a re-establishing of 

 the colour was evident from about the end of the first week onwards. A 

 mixture of fresh liver juice shaken up with pigment of suitable strength 

 would begin to become blue again in spite of the fact that the mixture 

 was covered by a layer either of toluene or of oil to the depth of an inch. 



In the routine observations, I made no attempt to eliminate the 

 oxidase of press-juice; but in one experiment Dr. Lovatt Evans and I 

 definitely arranged to exclude the physiological activity of that ferment. 

 Accordingly we kept a sealed up mixture of liver-juice and Prussian blue 

 at room temperature under an atmosphere of pure hydrogen in a com- 

 pletely reduced state for three and a half months. It never showed 

 the slightest re-blueing; on breaking the tube and adding HgOj, the con- 

 tents immediately became bright blue. Exposed to the air produced the 

 same result more slowly. Evidently the activity of the oxidase was 

 prevented expressing itself owing to there being no oxygen for it to deal 

 with. 



According to Spitzer, the vigour of oxidase declines post mortem, 

 whereas that of reductase increases for a time, but is possible that the 

 former phenomemon is the cause of the latter, the increase in the energy 

 of the reductase being only apparent and due to the diminution in that 

 of the oxidase working in the opposite direction. 



Dr. Vernon", fixing his attention on the tissue-oxidases, regards 

 reducing ferments as troublesome intruders into his experiments; I 

 however am forced to recognise oxidases as forming as much a part of 

 the cellular respiratory enzymic mechanism as are reductases. 



In some manner with which we are far from being fully acquainted, 

 catalase, oxidase and reductase are all acting simultaneously in the 

 living cells, carrying on the work of tissue-respiration. I have eliminated 

 the activity of the oxidase for a sufficiently long time to allow the 

 reductase untramelled activity; and consersely Dr. Vernon in his studies 



