BIOSYNTHESIS OF PENTOSES 



259 



GLYCOLYTIC ROUTE 



Fructose- 6-P 



HEXOSEMONOPHOSPHATE 

 OXIDATIVE PATHWAY 



Glucose- 6-P ^TPN 



X 



6-Phosphogluconolactone 



ATP 

 ADP 



D 



Sedoheptulose-7-P 



Fructose- 1, 6-P 

 i 



6-Phospliogluconate 



1U-TPN 

 -CO2 



^TPNH 

 Ribulose-5-P=^^:Ribose-5-P 



C> fragment (?) 



Dihydioxyacetone-3-P^= 

 t-DPNH 



, "^DPN 



a-Glycerophosphate 



=^Glyceraldehyde-3-P 

 DPN-\ 



DPNH^ 



1, 3- Diphosphogly cerate 



ADP 



3-Phosphoglycerate ATP 



2-Phosphoglycerate 



Phosphoenolpyruvate 

 ADP-J[ 

 ATP-> 

 Pyruvic acid 

 Fig. 5. The glycolytic and hexosemonophosphate oxidative pathways. 



different physiological conditions is still, however, chiefly a matter of con- 

 jecture. Englehardt and Sakov" suggested that the redox potential would 

 determine the route of carbohydrate metabolism, since phosphohexose 

 kinase was found to be very sensitive to O2 and various redox dyes. In the 

 living cell, a multiplicity of factors presumably regulate these metabolic 

 pathways including probably electrolyte distribution, O2 tension, and the 

 influence of hormones. A few attempts have, however, been made to assess 



61 W. A. Englehardt and N. E. Sakov, Biokhimiya 8, 9 (1943), quoted by F. Dickens 

 in "The Enzymes" (Sumner and Myrback, eds.), Vol. 2, p. 624. Academic Press, 

 New York. 



