L-lactate oxidase () is an enzyme that catalyzes the chemical reaction:
It belongs to the family of oxidoreductases (enzymes involved in redox reactions), specifically those acting on the group of donors with oxygen as acceptor. The systematic name of this enzyme class is (S)-lactate:oxygen 2-oxidoreductase. It employs one cofactor, flavin mononucleotide. The amino acid sequence of this enzyme is similar to that in lactate 2-monooxygenase, which converts lactate to acetate and carbon dioxide. The difference in the products formed has been ascribed to differences in the stability of an intermediate complex.
The enzyme was first isolated and characterised from the bacterium Aerococcus viridans. The relevant genes from Streptococcus iniae were subsequently cloned to allow further study. These developments have allowed the enzyme to be used in biosensors which measure the concentration of lactic acid in blood.
Tertiary structures have been solved for this class of enzymes, with the PDB accession code .