The enzyme 2-oxopent-4-enoate hydratase () catalyzes the chemical reaction:
This enzyme belongs to the family of lyases, specifically the hydro-lyases, which cleave carbon-oxygen bonds. The systematic name of this enzyme class is 4-hydroxy-2-oxopentanoate hydro-lyase (2-oxopent-4-enoate-forming). Other names in common use include 2-keto-4-pentenoate hydratase, OEH, 2-keto-4-pentenoate (vinylpyruvate)hydratase, and 4-hydroxy-2-oxopentanoate hydro-lyase. This enzyme participates in nine metabolic pathways: phenylalanine metabolism, benzoate degradation via hydroxylation, biphenyl degradation, toluene and xylene degradation, 1,4-dichlorobenzene degradation, fluorene degradation, carbazole degradation, ethylbenzene degradation, and styrene degradation.