Crystallographic study on the interaction of l-lactate oxidase with pyruvate at 1.9 Å resolution

l-Lactate oxidase (LOX) from Aerococcus viridans catalyzes the oxidation of l-lactate to pyruvate by the molecular oxygen and belongs to a large family of 2-hydroxy acid-dependent flavoenzymes. To investigate the interaction of LOX with pyruvate in structural details and understand the chemical mechanism of flavin-dependent l-lactate dehydrogenation, the LOX-pyruvate complex was crystallized and the crystal structure of the complex has been solved at a resolution of 1.90 Å. One pyruvate molecule bound to the active site and located near N5 position of FMN for subunits, A, B, and D in the asymmetric unit, were identified. The pyruvate molecule is stabilized by the interaction of its carboxylate group with the side-chain atoms of Tyr40, Arg181, His265, and Arg268, and of its keto-oxygen atom with the side-chain atoms of Tyr146, Tyr215, and His265. The α-carbon of pyruvate is found to be 3.13 Å from the N5 atom of FMN at an angle of 105.4° from the flavin N5–N10 axis.