274 EXISTENXE OF A REDUCLXG EXDO-EXZYME 



According to Spitzer. the vigour of oxidase declines 

 post mortem, whereas that of reductase increases for a time, 

 but it is possible that the former phenomenon is the cause of the 

 latter, the increase in the energy of the reductase being only- 

 apparent and due to the diminution of that of the oxidase 

 working in the opposite direction. 



Dr. Vernon, (^^j fixing his attention on the tissue-oxidases, 

 regards reducing ferments as troublesome intruders into his 

 experiments. I, however, am forced to recognzie oxidases as 

 forming as much a part of the cellular, respiratory, enzymic 

 mechanism as are reductases. 



It is in this connexion significant that the Cannizzaro 

 reaction — the simultaneous oxidation and reduction of 

 aldehydes — has been observed most frequently with liver 

 tissue in the presence of dilute sodium bicarbonate and oxygen. 



Possibly the "aldehydemutase" of Pamas is not one 

 enzyme but a mixture of oxidase and reductase P). 



In some manner with which we are far from being fully 

 acquainted, catalase. oxidase and reductase are all acting 

 simultaneoush" 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 conversely Dr. Vernon in his 

 studies on oxidase has had to make due allowance for the 

 presence of reducing substances. 



Dr. Vernon and also Prof. B. Moore(^^)have pointed out 

 several respects in which oxidase differs from reductase. 



It is perhaps too soon to formulate any theory of tissue 

 respiration, but when the scheme is outlined it must be one 

 taking cognizance of all the three respiratory types of enzymes 

 and not a scheme framed in terms of oxidase alone. 



Provisionally one might say that by reductase, oxygen is 

 abstracted from tissue-lymph ( more remotely from oxyhaemog- 

 lobin) and brought within the sphere of the activity of the 

 oxidase which applies to it the oxidation of the carbon, hydro- 



