hydratase

Hydratase is an enzyme that catalyzes the addition of water to carbon–carbon multiple bonds (hydration) or, less commonly, the reverse dehydration. In standard enzyme classification, hydrases are part of the lyase family (EC class 4), with hydratases designated as EC 4.2.1.x to reflect their role in water addition across unsaturated substrates.

Common examples include fumarate hydratase (fumarase), which hydrates fumarate to malate in the citric acid cycle, and enoyl-CoA hydratase (crotonase), which hydrates enoyl-CoA to 3-hydroxyacyl-CoA during fatty acid beta-oxidation. These enzymes are found across bacteria, plants, and animals and can often catalyze the reaction in either direction depending on substrate availability and cellular conditions.

Mechanistically, hydratases typically promote water addition via acid–base catalysis within the active site, and some require metal ions or cofactors to polarize water or stabilize intermediates. Structural diversity exists among hydratases; many function as dimers or larger oligomers and adopt different protein folds.

Biological role and significance include participation in central pathways such as the citric acid cycle and fatty acid degradation. Hydration reactions help convert substrates into forms that can enter subsequent metabolic steps, contributing to energy production and carbon flow. Defects in specific hydratases can disrupt metabolism and, in rare cases, be associated with disease states, reflecting their essential roles in cellular physiology.

Hydratases are also explored in biocatalysis for stereospecific or regioselective hydration of alkenes, illustrating their potential for synthetic applications in chemistry and biotechnology.