ROLE OF REDUCTASE IN TISSUE RESPIRATION 63 



(aldoses) the carbohydrate chains are capable of disintegrative 

 oxidation, and already aldehydases have been assumed. 



The fatty acids are certainly oxidised in the tissues after 

 being desaturated in the liver. The long carbon chains are 

 broken up at the /3-carbon atom at each oxidation until finally 

 /3-hydroxybutyric acid is obtained, which is ultimately oxidised 

 in the presence of sufficient carbohydrate to carbon dioxide and 

 water. If insufficient carbohydrate be present, then the acetone 

 group of bodies is excreted which is the chemical abnormality in 

 diabetes. 



Amino-acids are certainly oxidised after deamination, which 

 is itself regarded as enzymic. Amino-acids thus deaminated are 

 ordinary fatty acids which can then undergo the progressive 

 oxidative break-down to which these acids are liable. Lastly, 

 bodies of the purin group undergo oxidations within the 

 tissues, and specific enzymes are described which accomplish 

 these. 



These various oxidations in the tissues which are now 

 regarded as enzymic are thermogenetic and are entitled to be con- 

 sidered as making up internal respiration on its disassimilatory 

 side. We may, in fact, speak of tissue expiration, since the various 

 processes have for their object the excretion of waste-products. 

 The consensus of chemical opinion, then, is that tissue expiration 

 is dominated by intracellular ferments, and all that we claim at 

 present is that tissue inspiration should be so regarded. We 

 have evidence of a very powerful intracellular ferment which 

 brings active oxygen within the sphere of the oxidases. This is 

 the ferment already called reductase in 1899. We think that the 

 time has come to give it its specific name of hcemoglobinase, for 

 haemoglobin is the source of the oxygen it deals with, haemoglobin 

 is the substance reduced by it, haemoglobin is the natural substrate 

 or substance on which it normally acts. 



A comparatively recent observation by Dakin J is of interest 

 in this connection. " The oxidation of /3-hydroxybutyric acid to 

 aceto-acetic acid was shown by Dakin and Wakeman to be due 

 to an enzyme which could be roughly separated from liver tissue. 

 The action of the enzyme was not very vigorous, but was 

 markedly increased by the presence of oxyhasmoglobin. Oxy- 

 hemoglobin alone was entirely without action." It seems ex- 



1 Dakin, Oxidations and Reductions in the Animal Body. Dakin, Longmans, 

 1912, p. 23. 



