Bacteria develops the phosphoenolpyruvate (PEP):sugar phosphotransferase system (PTS) whose components participate in a variety of regulatory processes. Glucose-specific enzyme IIAGlc, a component of PTS, interacts with several target proteins, regulating their activity. Fermentation/respiration switch (FrsA) protein, one of IIAGlc-binding proteins, is known to increase glucose fermentation under oxygen-limited conditions. Here, we demonstrate that FrsA is a proficient enzyme that converts pyruvate to acetaldehyde and carbon dioxide in a cofactor-independent manner, which contrasts with the established notion that the decarboxylation of a-keto acids depends on a cofactor. According to the crystal structures, FrsA assumes the canonical a/b hydrolase structure but contains no catalytic machinery for hydrolytic reactions. Structure-based identification of three amino acids (Arg53, Asp203, and Arg272) critical for pyruvate decarboxylation, together with no requirement of cofactors in catalysis, leads us to propose a direct decarboxylation mechanism that is based on electrostatic repulsion. Furthermore, we show that IIAGlc enhances the enzymatic activity of FrsA by modulating the active site conformation, revealing the biological implication of complex formation between FrsA and IIAGlc.