cyclohydrolase

Cyclohydrolase refers to a class of enzymes that catalyze the hydrolytic opening of cyclic substrates. In these reactions, water is added to a ring-containing molecule, leading to ring cleavage and the formation of open-chain or rearranged products. The name describes the reaction type rather than a single, unified structural family, and cyclohydrolases are found in diverse biological contexts.

Reaction scope and mechanism vary among cyclohydrolases. They can act on cyclic esters (lactones), cyclic amides (lactams), or other ring systems, producing linear or differently structured products. The enzymes are typically hydrolases (enzyme class EC 3), but they belong to multiple structural families and folds, reflecting convergent evolution for ring-opening hydrolysis. Mechanistically, water acts as the nucleophile, and catalysis often involves acid-base residues in the active site, with some enzymes requiring metal ions such as zinc or manganese to aid catalysis.

Distribution and roles in biology are broad. Cyclohydrolases occur in bacteria, archaea, and eukaryotes and participate in various metabolic pathways, including vitamin and nucleotide metabolism, as well as the degradation or remodeling of cyclic compounds. In bacteria, certain cyclohydrolase activities are of interest as potential targets for antimicrobial strategies, given their role in essential metabolic routes. The enzymes are sometimes standalone proteins or part of larger, multifunctional complexes.

See also: hydrolases, lactonases, lactamases.