betaenolase

Beta-enolase, also known as enolase 3 (ENO3), is a muscle-specific isoform of the glycolytic enzyme enolase. In glycolysis, enolase catalyzes the reversible dehydration of 2-phosphoglycerate to phosphoenolpyruvate, a key step that ultimately contributes to ATP production. Beta-enolase functions in the cytosol of skeletal muscle cells and, to a lesser extent, cardiac muscle, and it typically forms a homodimer that requires Mg2+ as a cofactor.

In humans, enolase exists as three isoforms: alpha-enolase (ENO1, ubiquitous), beta-enolase (ENO3, muscle), and gamma-enolase (ENO2, neuronal). The beta-enolase protein is encoded by the ENO3 gene. The enzyme is expressed predominantly in developing and mature muscle, and its expression correlates with muscle differentiation and energy demand. As a muscle-specific enzyme, beta-enolase contributes to the glycolytic flux that supports muscle contraction and endurance.

Clinical significance of beta-enolase is most evident in cases of ENO3 deficiency, a rare inherited metabolic myopathy. Affected individuals typically present with exercise-induced muscle weakness, cramps, and myoglobinuria following strenuous activity. Diagnostic evaluation may reveal reduced enolase activity in muscle tissue and genetic testing can identify pathogenic ENO3 variants. Management is supportive, focusing on energy balance, avoiding extreme exertion, and symptom-based care. Research continues to explore the full range of beta-enolase’s cellular roles and its involvement in metabolic muscle diseases.