DISCUSSION ON PHOSPHORYLATION 193 



decomposition of this ester in living yeast. Indeed the occurrence of 

 the same phosphorylated intermediaries in hving cells as in extracts 

 is clearly demonstrated by the experiments of Miss Macfarlane, 

 Werkman, Dische, and others. But the adenylpyrophosphatase, 

 which is responsible for the fermentation of hexosediphosphate in the 

 absence of a stoichiometric amount of phosphate acceptors, is weak- 

 ened even by drying the yeast, more by incubation and extraction 

 of the dried yeast, and it can be completely destroyed by precipita- 

 tion with acetone. 



On the other hand, we may assume that in the living cell excess 

 phosphorylation of sugar occurs in connection with growth. The 

 starting point of these syntheses may be some other ester instead of 

 hexosediphosphate; nevertheless the autocatalytical increase of this 

 ester in a fermenting yeast extract can be taken as a good model 

 for material growth brought about by the energy of fermentation; 

 indeed, such an extract, containing sugar, will not start fermentation 

 unless it is "inoculated" by a trace of hexosediphosphate, which then 

 "grows" at the expense of sugar. 



2. At least some of the experiments of different authors quoted by 

 Dr. Lipmann seem not too reliable in regard to abnormally high 

 oxidation quotients. I refer especially to cases with Qo, values of 

 to 1. Under such conditions the manometric method is not accurate 

 enough, and a completely stationary state during the time of the 

 experiment is not assured. 



Furthermore, it seems to me, the distribution of oxidized to re- 

 duced cozymase in toto cannot be used as the basis for deciding 

 how far the hydrogen transfer by means of cozymase is affected by 

 respiration. This transfer occurs by means of the bound cozymase of 

 specific enzymes, and the oxidative state of such a compound may 

 well be altered by the oxygen transfer from oxidative catalysts with- 

 out an appreciable change in the overall distribution of oxidized 

 to reduced cozymase. 



3. The interesting finding of Dr. Kalckar that the action of hexo- 

 kinase of yeast is supplemented by a heat-stable enzyme of muscle, 

 "myokinase," by which adenosinediphosphate transfers its labile 

 phosphate group to glucose, points to a difference, already well 

 known, between the enzymes in muscle and yeast preparations. 

 While the former (extract, acetone powder, etc.) retains the ability 

 to use adenylic acid as the phosphorylating coenzyme even after 

 long dialysis and "ageing," in yeast preparations the reaction step, 



(2) P-acceptor + adenosinediphosphate ±5 P-acceptor — phos- 

 phate + adenylic acid. 



