250 



Van R. Potter and Hermann Niemeyer 



oxidize TPNH in the performance of the pentose cycle (Bon- 

 signore, PontremoH and Vergnano, 1957; Kinoshita, 1957; 

 Cahill et al., 1958; Wenner and Mohterno, 1958). 



Some of the inter-relationships between several of the 

 oxidation-reduction equilibria more directly concerned with 

 carbohydrate metabolism and with the system used in our 

 experiments are shown in Fig. 16. One must bear in mind, 

 however, that there exist, both in aerobiosis and in anaero- 

 biosis, several alternative pathways for hydrogen and for the 



GLUpOSE 



P-Glyceraldehyde 



U 

 Di-P-Glyceric 



t 



GLUCOSE ^p^^ 



Glucose-6-P S^-^ti 



6-P-Gluconic^ '^'"^ 



t ^^3 



Ribulose-5-P 



oc-GIycero-P 

 Dihydroxyacetone-P 



Cytochr. red 



t \ 

 Cytochr. OX 



Mitoch^ t i Mitoch \ 



H.0 

 2 



Fig. 16. Scheme to show some of the inter-relationships between different 

 oxidation-reduction systems related directly to carbohydrate metabolism. 



other metabolites of this scheme, but one has to realize that it 

 would be impossible to try to integrate all these possibilities 

 in a single figure. 



The enhancement of glucose consumption observed in some 

 experiments is understandable if one considers such a relation- 

 ship of enzyme activities that would permit the shift of a 

 fraction of G-6-P to the pentose cycle, enough to increase 

 glucose uptake and to decrease lactic acid production, but 

 still unable to produce enough inhibitor to act upon the iso- 

 merase. This shift of G-6-P metabolism from the glycolytic 

 channel to the pentose cycle pathway was postulated by 



