Explanation for the apparent lack of ouabain inhibition of pyruvate production in hemolysates: the "backward" PGK reaction.

The concept that ouabain-sensitive membrane (Na+ + K+)-ATPase-generated adenosine diphosphate (ADP) preferentially serves as the substrate for the phosphoglycerate kinase (PGK) step of erythrocyte glycolysis has been reexamined. Membrane ATPase readily provides ADP for and utilizes ATP generated in the pyruvate kinase (PK) step and is ouabain sensitive. Earlier reports in the literature, which have suggested that in hemolysates the ATPase reaction facilitating the PK reaction is ouabain-insensitive, are reinterpreted: in crude hemolysates ADP generated in the "backward" PGK reaction can account for these data. We conclude that there is no convincing evidence of selective linkage of (Na+ + K+)-ATPase with the PGK reaction.