Transissomerases

Transissomerases are a proposed class of enzymes that catalyze the interconversion between trans and cis geometries of substrate molecules. The term is not uniformly used in standard enzyme nomenclature; much of the literature uses cis-trans isomerases (EC 5.2) or, for peptide bonds before proline, peptidyl-prolyl cis-trans isomerases (PPIases; EC 5.2.1). When the term transissomerase appears, it is typically to emphasize a role in geometric rearrangements that alter a substrate’s conformation and often its activity.

Mechanistically, transissomerases show diverse strategies depending on the substrate. In polypeptides, the archetype is the PPIase, which accelerates cis–trans isomerization of peptide bonds preceding proline and thereby influences protein folding and signaling. In small molecules and other macromolecules, related activities may stabilize a high-energy transition state or provide a binding environment that biases one geometry over another. Cofactor usage and structural folds vary across enzymes described as transissomerases.

Biologically, cis–trans isomerization governs folding pathways, allosteric regulation, and maturation of many proteins, and can influence membrane dynamics and metabolic flux. While PPIases are the best-characterized exemplars of this activity, broader discussions of transissomerases acknowledge overlap with established isomerase families and note that the term is not universally adopted.

See also: isomerase, cis-trans isomerase, peptidyl-prolyl cis-trans isomerase.