pH‐Dependent Changes of 2,3‐Bisphosphoglycerate in Human Red Cells during Transitional and Steady States in vitro

Abstract

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. The results indicate that 2,3‐bisphosphoglycerate phosphatase breaks down 2,3‐bisphosphoglycerate nearly independent of pH at a rate of 480 μmol 2,3‐bisphosphoglycerate × 1 cells−1× h−1. 2,3‐Bisphosphoglycerate mutase is practically completely inhibited below pH 6.9. An increased Km 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. 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. 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. Copyright © 1977, Wiley Blackwell. All rights reserved