isomerasen

Isomerasen, or isomerases, are enzymes that catalyze the rearrangement of atoms within a single molecule to form isomers. They change the arrangement of atoms or the stereochemistry of a molecule without altering its overall chemical formula. Isomerases are grouped in the Enzyme Commission (EC) classification under EC class 5, which is dedicated to isomerization reactions.

The reactions catalyzed by isomerases include racemization and epimerization, where the configuration at a stereogenic center is inverted or altered at a single carbon; cis-trans (geometric) isomerization, which converts between different geometric forms around a double bond or within rigid ring systems; and various intramolecular rearrangements that reorganize carbon skeletons without adding or removing atoms. These reactions are pivotal for metabolic flexibility, allowing pathways to proceed through alternative intermediates or to prepare substrates for subsequent enzymatic steps.

Notable examples include glucose-6-phosphate isomerase (GPI), which interconverts glucose-6-phosphate and fructose-6-phosphate in glycolysis; triose phosphate isomerase (TIM), which equilibrates glyceraldehyde-3-phosphate and dihydroxyacetone phosphate; and alanine racemase, which converts L-alanine to D-alanine, a step relevant in bacterial cell wall synthesis. Peptidyl-prolyl cis-trans isomerases (PPIases) catalyze the cis-trans isomerization of peptide bonds adjacent to proline residues, facilitating protein folding.

Isomerases are essential across organisms and play diverse roles in metabolism, DNA repair, and protein maturation. Their activity often integrates with other enzyme systems to regulate flux through metabolic networks and ensure proper biomolecule function.