8 A SYMPOSIUM ON RESPIRATORY ENZYMES 



since the oxidized molecule also had to be phosphorylated, altogether 

 twelve molecules of phosphates are taken up for one molecule glucose 

 or twelve oxygen atoms consumed. Therefore every step of glucose 

 oxidation consisting in an oxidoreduction between cozymase and an 

 oxidizable intermediary is coupled with phosphorylation. Not only is 

 this true for the two steps where it is already known, i.e., the oxida- 

 tion of phosphoglyceraldehyde and that of pyruvic acid, in which 

 Lipmann discovered acetylphosphate as the primary product of 

 oxidation (18), but for every such step an energy-rich phosphate 

 bond is created in adenosinetriphosphate, which enables a synthetic 

 step to take place. 



The experiments of Belitzer and Tzibakowa are a little dijBFerent, 

 because they added creatine to cut muscle and obtained under these 

 conditions a synthesis of creatinephosphate when lactate, pyruvate, 

 or the four-carbon acids of the Szent-Gyorgy cycle were oxidized. 

 At the most two molecules of creatinephosphate were formed for 

 every oxygen atom taken up. Although the presence of creatine 

 diverts the pathway of synthesis from carbohydrate, the experiments 

 are important in that they demonstrate the uptake of two molecules 

 of phosphate by way of adenosinetriphosphate for one atom of 

 oxygen consumed; this relationship is comparable to the synthesis 

 of creatinephosphate in muscle extract, where two steps of glycolysis 

 are involved in the transfer of phosphate, namely, the oxidoreduction 

 and the dephosphorylation of phosphopyruvic acid (19). 



Moreover, the reaction studied by Belitzer is closely analogous to 

 the recovery period of the living muscle, especially a muscle which is 

 only slightly fatigued. Here, during oxidative recovery, the oxidation 

 serves mostly for the resynthesis of creatinephosphate, and to a small 

 extent for that of glycogen. If two molecules of creatinephosphate are 

 synthesized for every atom of oxygen taken up, then about 40 per 

 cent of the combustion heat of sugar or lactate is consumed for the 

 endothennic synthesis, a result which comes very close to the 

 efficiency of the oxidative recovery in the living muscle.* 



But to return from this digression to the significance, already men- 

 tioned, of the experiments for the theory of carbohydrate cycles. 

 One objection may be raised against this interpretation of the Pas- 

 teur effect. Many cases are known where the respiration remains 

 quantitatively the same, while the effect of the respiration on the 



* Actually the same ratio of two molecules of creatinephosphate syntliesized 

 for one atom of oxygen taken up was found by O. Meyerhof and D. Nachman- 

 .sohn (Biochem. Z., 222, 1, 1930) during recovery of a partially fatigued muscle. 



