Hydrolases

Hydrolases are a broad class of enzymes that catalyze hydrolysis reactions, cleaving chemical bonds by adding water. They constitute one of the six main classes of enzymes in the enzyme commission (EC) classification, designated EC 3. They act on diverse substrates, including proteins, lipids, carbohydrates, nucleic acids, and esters.

Key families include proteases (peptidases) that hydrolyze peptide bonds; lipases that cleave ester bonds in fats; glycosidases that split glycosidic bonds in carbohydrates; nucleases that cleave phosphodiester bonds in nucleic acids; and phosphatases that remove phosphate groups. Mechanistically, hydrolases often rely on acid-base catalysis and, in many cases, covalent intermediates. Some, such as serine proteases, use a catalytic triad to activate a nucleophile, while metallohydrolases employ metal ions (for example zinc) to activate water for bond cleavage.

Physiological roles span digestion, metabolism, and cellular remodeling. In biology, hydrolases participate in protein turnover, nutrient acquisition, and signaling. Industrial and medical applications are broad: digestive enzyme supplements, detergent formulations, processing of food and biofuels, and targeted drugs that inhibit specific hydrolases (for example, protease inhibitors in medicine). Hydrolases are found in diverse cellular contexts, including lysosomes, periplasmic spaces, and extracellular environments, and they exhibit a wide range of pH optima and substrate specificities. Regulation occurs through gene expression, secretion as inactive precursors, subcellular localization, and inhibitors that modulate activity.