Il6 PLANT RESPIRATION 



theory of respiration. They could rather be used in favor of the 

 assumption that a primary anaerobic cleavage of sugar is 

 necessary for sugar respiration.^ 



An entirely different theory of the oxidation processes has 

 been developed by Wieland.- According to his view, the oxy- 

 gen of water is utilised for all biological oxidations. The atmos- 

 pheric oxygen only serves to bind the hydrogen of the water. 

 In general Wieland supposes that oxidations are always accom- 

 panied by simultaneous reductions, for always the hydrogen 

 and not the molecular oxygen is said to be activated. The latter 

 is said to remain entirely passive and to form no unsaturated 

 molecules. According to Wieland oxidation is to be traced 

 solely to the formation of active atomic hydrogen. If the 

 active hydrogen of the water is tied up by a hydrogen acceptor 

 the residual unsaturated oxygen of the water can unite with 

 various substances. Either atmospheric oxygen or various 

 other substances could serve as hydrogen acceptors. In the 

 latter case it is possible to carry out various oxidations and 

 reductions with air excluded: Thus Wieland has shown that 

 acetic acid fermentation of ethyl alcohol by atmospheric oxy- 

 gen, commonly thought to be an oxidation, proceeds smoothly 

 in the presence of methylene blue or w-dinitrobenzol with 

 oxygen entirely excluded. According to Wieland a state of 

 equilibrium is therefore precluded under these conditions 

 because the active hydrogen is permanently bound up. As 

 for the manner of action of peroxidases, Wieland assumes that 

 ■ these enzymes only activate the hydrogen of the polyphenols 



' The latest discovery of Warburg and Yabusoe, according to which fructose undergoes 

 oxidation in the presence of phosphates, is interesting. Cj. Warburg, O. und M. Yabusoe. 

 Biochem. Z. 146: 380. 1924; Spoehr, H. A. Jour. Amer. Chem. Soc. 46: 1494- 1924. 

 However, this oxidation is so feeble that it can not serve as the basis of normal respiration. 

 On this point (-/. Meyerhof, O. und K. Matsuoka. Biochem. Z. 150: i. 1924. [The latter 

 have confirmed and augmented the work of Warburg and Yabusoe. The presence of traces 

 of iron in a certain form is said to be responsible for the slow but regular oxidation of fructose 

 (but not glucose) al 37° and in pure oxygen. These experimental conditions and the absence 

 of any effect on glucose — the more common source of respiratory energy — weakens the 

 argument for the general application of Warburg's suggestion. It is also true that a careful 

 demonstration of the catalytic action of iron for the oxidation of fructose has been made 

 only with alkaline solutions, whereas fructose is oxidised in neutral solutionsof phosphate 

 in Warburg's experiments (c/. Wind, F. Biochem. Z. 159: 58-67. 1925)- It would seem 

 that too little consideration was given to the possible catalytic effect of the phosphate. Cf. 

 editorial note k, page 126.] 



2 Wieland, H. Ber. d. chem. Ges. 45: 2606. 1912; 46: 3327. 1913; 47 : 2085. 1914; 

 55: 3639. 1922. 



