Anaerobic Glycolysis and Glycogenolysis do not Release Protons and do not Cause Acidosis

Background: A metabolic pathway is composed of a series of enzymatic steps, where the product of each reaction becomes the substrate of the subsequent one. We can summarize the single reactions to obtain the overall equation of the metabolic pathway, suggesting its role in the metabolic network. Objective: In this short review, we aim at presenting our present knowledge on the biochemical features underlying the interrelation between acidosis occurring during anaerobic muscle contraction and the glycolytic and glycogenolytic pathways. We emphasize that both pathways per se are not acidifying processes. Conclusion: The review emphasizes the following points: i) The importance that single reactions, as well as the overall equation of a metabolic pathway, are balanced; ii) Unbalanced reactions lead to unbalanced overall equations, whose functions cannot be correctly understood; iii) Glycogen acts as the major fuel for muscle anaerobic contraction. Anaerobic glycogenolysis not only does not release protons, but it also consumes one proton; iv) When dealing with metabolic acidosis, it should be always recalled that protons are released by muscle ATPase activity, not by glycolysis or glycogenolysis.