The enzyme maleate 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 (R)-malate hydro-lyase (maleate-forming). Other names in common use include <small>D</small>-malate hydro-lyase, malease, and (R)-malate hydro-lyase. This enzyme participates in butanoate metabolism.