a class of enzymes that catalyze reactions of hydrolytic decomposition (with the participation of water) of intramolecular bonds (hydrolysis). Hydrolases are widespread in plant and animal cells. They participate in processes of metabolism of proteins, nucleic acids, carbohydrates, lipids, and other biologically important substances. Depending on the type of bond hydrolyzed, hydrolases are divided into a number of subclasses: hydrolases acting on ester bonds (for example, lipase), glucoside bonds (amylase), peptide bonds (pepsin), and acid-anhydride bonds (adenosine triphosphatase).

By their chemical nature, most hydrolases are simple proteins. The presence of unaltered sulfhydryl groups (SH—) with a definite place in the polypeptide chain is necessary for the appearance of their catalytic activity. A number of hydrolases are produced in crystalline form (urease, pepsin, trypsin, and chymotrypsin). The mechanism of the catalytic action of some hydrolases that have been studied includes the addition of an enzyme, with decomposition of the substance followed by splitting off of the reaction products and liberation of the enzyme. It has been shown that in the mechanisms of enzymatic hydrolysis there is much in common with the action mechanism of transferase and that some hydrolases can transfer the groups being split off not only to water but also to other molecules.