isoenzyme

One of a group of enzymes that catalyze the same reaction but may be differentiated by variations in physical properties, such as isoelectric point, electrophoretic mobility, kinetic parameters, or modes of regulation; e.g., lactate dehydrogenase, a tetramer composed of varying amounts of α and β subunits ( i.e., 4α, 3α + 1β, 2α + 2β, 1α + 3β, and 4β). SYN: isozyme.

- creatine kinase isoenzymes the isoenzymes of creatine kinase. Creatine kinase is a dimer with M (muscle) and/or B (brain) subunits; it exists in three i. forms: CK-MM, the predominant form, found primarily in skeletal muscle; CK-MB, found in cardiac muscle, tongue, diaphragm, and in small amounts in skeletal muscle; and CK-BB found in the brain, smooth muscle, thyroid, lungs, and prostate. Elevations detected by electrophoresis or other methodologies can be used to help in the differential diagnosis of a variety of disease states, with CK-MB elevations as an important marker following myocardial infarctions, elevations in CK-MM an indicator of muscle disease, and increases in CK-BB an occasional finding following brain infarcts, bowel infarcts, or in the presence of certain malignancies.

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iso·en·zyme -'en-.zīm n any of two or more chemically distinct but functionally similar enzymes called also isozyme

iso·en·zy·mat·ic 'ī-sō-.en-zə-'mat-ik, -zī- adj

iso·en·zy·mic -en-'zī-mik adj

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(isozyme)

n.

a physically distinct form of a given enzyme. Isoenzymes catalyse the same type of reaction but have slight physical and immuno-logical differences. Isoenzymes of dehydrogenases, oxidases, transaminases, phosphatases, and proteolytic enzymes are known to exist.

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iso·en·zyme (i″so-enґzīm) isozyme.