112 PLANT RESPIRATION 



Thus the oxidising agencies of the protoplasm, previously 

 termed "oxidases," according to the investigations of Bach, 

 Chodat and their adherents, are nothing but systems of oxygen- 

 ases and peroxidases.^ At present it is not known whether the 

 increase of the potential of the oxygenase in the living cell 

 occurs but once or repeatedly. In any case the latter assump- 

 tion is not precluded. Thus Bodlander^ expresses his opinion 

 on the subject as follows: "By means of the active oxygen of 

 superoxide, substances which are oxidised with difficulty are 

 not entirely oxidised to carbon dioxide and water. Hence 

 substances which are easily oxidised and which thereby effect a 

 further activation of oxygen could arise from them. Of this we 

 have an example in the alcohols which of themselves are only 

 slowly oxidised by free oxygen but which, by means of activated 

 oxygen, pass over into aldehydes which by their autoxidation 

 bring about the oxidation of other inactive substances." 



Another conclusion which can be drawn from recent investi- 

 gations of biochemical processes is that these processes are 

 apparently not to be traced to enzyme action but to chemical 

 induction (coupled reactions). Engler and Herzog- express 

 their opinion that the importance of enzymes in biological 

 oxidations is strongly overrated: "In any case it would be 

 entirely precipitous to include the autoxidisable substances 

 among the enzymes; at least the subordination of the agencies 

 called oxidases under the true enzymes in the sense of catalysts 

 is perhaps to be refused. Apparently on the contrary, the fur- 

 ther, study of physiological oxidation already shows that the 

 dominant significance to be ascribed to them to-day as a result 

 of biochemical study, is not that of an enzymatic process, but 

 that the coupled reactions are to be sought as new motives to 

 which the organism also owes its peculiar character of the 

 chemical regulatory mechanism." 



' Bodlander. he. cil. 



- Engler, A. und Herzog. Z. f. physiol. Chem. 59: 375. 1909. 



' The most important objections to this view are those stated by Moore and 

 Whitley (Biochem. Jour. 4: 136. 1909), who doubt the presence of an oxygen- 

 ase, and by Mrs. Onslow (Biochem. Jour. 13: 1-9. 1919; 14: 535-547- 1920) 

 who differs in certain details. On the other hand, new support to the theory is to 

 be found in the work of Gallaghar (Biochem. Jour. 17:515-529. 1923 and 

 later numbers). — Ed. 



