Catalytic sites of hydrolases: structures and catalytic cycles

The applications of various bioinformatics methods and databases to the analysis and classification of proteins and search for active sites of enzymes are considered. The published data on the structures of active sites and mechanisms of action of hydrolases are analysed. It is emphasised that all of the known hydrolases can be divided into four groups according to the types of catalytic site which differ in the mechanisms of water activation. The mechanisms of water activation by catalytic groups in the active sites of hydrolases are discussed and the schemes of catalytic cycles characteristic of classical types of active sites of these enzymes are considered. Using glycosyl hydrolases and serine hydrolases as examples, it is demonstrated that different proteins possess common catalytic sites and mechanisms of action. The role of aspartic acid and histidine in the activation of hydrolase substrates and the role of structure-forming acids (glycine, proline, cysteine) in the structural organisation of the catalytic sites are considered.