Glycolysis-dependent Exchange of Diphosphopyridine Nucleotide-3H in Red Blood Cells and Ascites Cells

Abstract

L-Lactate-2-3H undergoes loss of tritium into water when incubated with red cells.Since lactate is not lost, this is an exchange.The exchange is stimulated lo-fold by glucose and this is reversed by iodoacetate.The tritium of glucose-4-3H, which would be expected to produce lactate-2-aH in glycolysis, is found in water.This exchange is not prevented by iodoacetate.From these results it is proposed that exchange detritiation of lactate occurs through the aldolase reaction, as follows: Lactate-2-H* -s DPNH* -7 glyceraldehyde-3-P-l-H* -D pyruvate 1,3-di-P-glycerate dihydroxyacetone-P-l-H* + H*OH catalyzed by lactate dehydrogenase, glyceraldehyde-P dehydrogenase, triose-P isomerase, and fructose-di-P aldolase.Loss of aH from lactate in ascites tumor cells occurring in the absence of glucose is largely inhibited by CO or Amytal.Upon addition of glucose the detritiation of lactate continues at about the same rate despite the inevitable dilution of the DPNaH pool by glycolytic DPNH, thus suggesting that a stimulation of DPNaH exchange has occurred as well.The detritiation in the presence of glucose is largely insensitive to amytal and CO, but is depressed by iodoacetate and AsOr, suggesting that the role of glucose in the detritiation of lactate is to provide glycerate-1 ,3-di-P in the above mechanism.The present study began as an attempt to use glucose-1-3H and -3-3H to determine the path of oxidation of TPNH generated in the glucose-6-P dehydrogenase and 6-phosphoglu-