isomerasa

Isomerase, sometimes referred to as isomerasa in some languages, is a class of enzymes that catalyze the rearrangement of atoms within a molecule to form isomers. These reactions change the spatial arrangement or connectivity of atoms without altering the molecular formula, and they play a central role in many metabolic pathways.

The enzyme commissions classification places isomerases in EC class 5. Subgroups include racemases and epimerases (5.1), cis–trans isomerases (5.2), and intramolecular transferases or mutases (5.3). Together, these enzymes enable transformations such as converting one stereoisomer into another, interconverting aldoses and ketoses, or moving functional groups within a molecule. Examples include triose phosphate isomerase, which interconverts dihydroxyacetone phosphate and glyceraldehyde-3-phosphate in glycolysis; glucose-6-phosphate isomerase, which converts glucose-6-phosphate to fructose-6-phosphate; ribose-5-phosphate isomerase, which interconverts ribose-5-phosphate and ribulose-5-phosphate in the pentose phosphate pathway; and phosphoglucomutase, which shifts a phosphate group between glucose-1-phosphate and glucose-6-phosphate. Racemases such as proline racemase catalyze changes in stereochemistry around a specific carbon.

Mechanistically, isomerases often operate via acid–base catalysis, transient enol or enolate intermediates, or metal-ion–assisted steps, and may require cofactors or specific active-site residues. They are essential for metabolic flexibility, enabling efficient substrate utilization and the interconversion of metabolites to fit cellular needs.