dehydrataseisomerase

Dehydrataseisomerase is not a formal enzyme class in the standard enzyme nomenclature. In some writings it is used as a descriptive term for proteins that exhibit both dehydratase and isomerase activities, either within one polypeptide with two catalytic domains or as two linked activities in a pathway. The defining feature would be two sequential chemical transformations: first a dehydration reaction that removes water to generate an unsaturated intermediate or rearranged substrate, followed by an isomerization that rearranges atoms to a different structural isomer.

Mechanistically, dehydration often proceeds via acid-base catalysis and can create enol, carbonyl, or carbocation–like intermediates that enable subsequent rearrangements. The isomerization step may involve shifting a functional group, such as epimerization, cis–trans isomerization, or a carbon skeleton rearrangement, without a change in oxidation state.

Biological roles for such bifunctional activities could include streamlined flux through a metabolic pathway, where the dehydration and subsequent isomerization occur in close succession to optimize efficiency or regulation. In practice, when both activities are present, enzymes are typically described by their separate activities, or annotated with multiple functional domains and distinct EC numbers rather than a single, official EC entry.

Because dehydrataseisomerase is not an official classification, researchers generally refer to the individual activities or to the combined function in descriptive terms, rather than as a standalone enzyme category.