A systematic study of the pH-dependent changes in the range 6.6 -7.4 of 2,3-bisphosphoglycerate and the adenine nucleotides was performed in the presence and absence of glucose during transitional and steady states.1. The results indicate that 2,3-bisphosphoglycerate phosphatase breaks down 2,3-bisphosphoglycerate nearly independent of pH at a rate of 480 pmol 2,3-bisphosphoglycerate x 1 cells-' x h-'. 2,3-Bisphosphoglycerate mutase is practically completely inhibited below pH 6.9. An increased K, 2,3-bisphosphoglycerate is postulated. The 2,3-bisphosphoglycerate level in the presence of glucose reaches a pH-dependent steady state after about 18 h in keeping with theoretical predictions.2. The constancy of the adenine nucleotides in the presence of glucose regardless of the rate of glycolysis indicates a close coupling between ATP formation and breakdown. The decline of the sum of adenine nucleotides appears to be determined by the rate of AMP breakdown.3. The share of the 2,3-bisphosphoglycerate bypass in the steady state decreases from 24% at pH 7.4 to 12 % at pH 7.04. The initially decreased glycolysis at low pH values increases in long-term experiments with lower 2,3-bisphosphoglycerate levels. The formation of pyruvate corresponds to the breakdown of 2,3-bisphosphoglycerate after consumption of an unknown reducing substance.The original observations of a breakdown of 2,3-P,glycerate [l -31 at low pH values, both in uivo and in vitro have been confirmed repeatedly. Nevertheless a systematic study of this phenomenon has not been performed so far, nor has its mechanism been elucidated. At present there is a lack of understanding by what mechanism steady state concentrations of 2,3-P,-glycerate are established under various physiological and pathological conditions. The experiments carried out so far in vitro do not permit valid extrapolations to the conditions in vivo. The purpose of the present study was an investigation of the pH-dependent kinetics of the changes of 2,3-P2glycerate both during transitional and steady states. It included an assessment of both the over-all flux through glycolysis as well as through the 2,3-P2glycerate bypass. In addition the behaviour of the adenine nucleotides was studied.Abbreviations. 2,3-P2glycerate, 2,3-bisphosphoglycerate; 1,3-Enzymes.

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