Role of TPN in Control of Glycolysis 



243 



Effect of TPNH 



If TPN exerted a direct inhibition on glycolysis to bring 

 about a Pasteur effect, it might be expected that TPNH 

 would not have a similar effect. The experimental data 

 showed, however, that TPNH inhibited glycolysis in this 

 system. As with TPN, its effect was less constant on glucose 

 uptake and sometimes an increase was observed. The effect 

 was, in general, less than that of TPN. 



Effect of degradative products — The effect of TPNH was com- 

 plicated by the fact that commercial preparations often have 



-A GLUCOSE 



+A LACTATE 



-AORTHOPHOS- 

 PHATE 



1 



Ml 



Fig. 9. Effect of a degradative product of TPNH on glycoly- 

 sis. The composition of the medium was similar to that of 

 Fig. 1 . 3 [jLM TPNH or the equivalent amount of the degrada- 

 tive product (TPNH-X) when indicated, pH 7-4. 



degradative products as contaminants, as shown by spectro- 

 photometric studies. In fact, the ratio of absorbance at 260 

 m(x to that at 340 vci\L varied from 8 • 4 to 4 or higher in many 

 preparations, instead of being 2-4. The minimum absorbance 

 between the peaks was also abnormal, with a displacement 

 from 292 mjji to 305 m\L. These characteristics correspond to 

 the presence of degradative products and they could be 

 important, because it was shown that the degradative product 



