Isomerase

In biochemistry, an isomerase is an enzyme that catalyzes the structural rearrangement of isomers. Isomerases thus catalyze reactions of the form


 * A &rarr; B

where B is an isomer of A.

Nomenclature
The names of isomerases are formed as "substrate isomerase" (for example, enoyl CoA isomerase), or as "substrate type of isomerase" (for example, phosphoglucomutase).

Classification
Isomerases have their own EC classification of enzymes: EC 5. Isomerases can be further classified into six subclasses:
 * EC 5.1 includes enzymes that catalyze racemization (racemases) and epimerization (epimerases)
 * EC 5.2 includes enzymes that catalyze the isomerization of geometric isomers (cis-trans isomerases)
 * EC 5.3 includes intramolecular oxidoreductases
 * EC 5.4 includes intramolecular transferases (mutases)
 * EC 5.5 includes intramolecular lyases
 * EC 5.99 includes other isomerases (including topoisomerases)