What does isoenzyme mean?
An isoenzyme is one of two or more forms of an enzyme that carry out the same biochemical reaction but differ in molecular structure, such as their amino-acid sequence, charge, or electrophoretic behaviour. The word is especially useful in biochemistry, genetics, pharmacology, and clinical chemistry, where identifying the particular form present in a tissue or blood sample can reveal biological differences that a general enzyme test does not show. For example, laboratories may compare isoenzyme profiles to distinguish healthy tissue from damaged or diseased tissue. The term is also closely associated with isozyme, an alternative name that is frequently used for the same concept. Although isoenzymes perform equivalent catalytic functions, their differing properties can affect reaction rates, stability, or responses to biological regulation. In less technical writing, “enzyme” is usually more appropriate.
nounAn enzyme that performs the same catalytic function as another enzyme but has a different molecular structure or amino-acid sequence. Isoenzymes can be distinguished by their physical properties, electrophoretic mobility, or reaction rates.
- An enzyme that catalyses the same reaction as another enzyme but differs in molecular composition or physical properties.
"The laboratory compared the isoenzyme profiles of healthy and diseased tissue samples."
"Researchers identified the particular isoenzyme responsible for the abnormal enzyme activity."
"Different tissue types may contain distinct isoenzymes in different proportions."
The plural is formed by adding -s to the singular form.
"The researchers compared several isoenzymes found in the blood."
The prefix iso- does not mean “different” here; it means “equal,” because isoenzymes perform the same catalytic work.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does isoenzyme come from?
The word was formed in the early 20th century from the combining form iso-, meaning “equal,” and enzyme, from Greek zymē, meaning “leaven” or “ferment.” The naming reflects the fact that these enzyme forms perform the same catalytic task. The related scientific terms enzymatic, enzymology, and enzyme all share this Greek root for leavening or fermentation.
Related word forms
How isoenzyme is actually used
This is primarily a technical term in biochemistry, genetics, clinical chemistry, and molecular biology. It is closely related to the alternative term isozyme, and the two names are often used interchangeably.
Easily confused with isoenzyme
An isoenzyme is an alternative molecular form of an enzyme, whereas an isomer is a chemical compound with the same molecular formula but a different arrangement of its atoms.