Catalyzes the reversible conversion of 2-phosphoglycerate into phosphoenolpyruvate. It is essential for the degradation of carbohydrates via glycolysis. (2R)-2-phosphoglycerate = H2O + phosphoenolpyruvate The covalent binding to the substrate at Lys-339 of a small fraction of enolase causes inactivation of the enzyme, and possibly serves as a signal for the export of the protein (PubMed:15003462). Citrate acts as a non-competitive inhibitor for both forward and reverse reactions, probably by chelating Mg(2+) (PubMed:22198292). Carbohydrate degradation; glycolysis; pyruvate from D-glyceraldehyde 3-phosphate: step 4/5. Homooctamer. Component of a possible RNA degradosome complex composed of rny, rnjA, rnjB, pnp, pfkA and eno (PubMed:19193632) (although rnjA and rnjB's presence is unclear). Fractions of enolase are present in both the cytoplasm and on the cell surface. The export of enolase possibly depends on the covalent binding to the substrate at Lys-339; once secreted, it remains attached to the cell surface. Phosphorylated during sporulation. Belongs to the enolase family.