Isozyme

Definition

One of multiple enzyme variants that catalyze the same biochemical reaction but differ in amino acid sequence, kinetic properties, or regulatory control. Isozymes enable tissue-specific or developmental-stage-specific metabolic regulation and serve as powerful genetic markers in population and evolutionary studies.

Etymology

From Greek isos (equal) + enzyme, reflecting identical catalytic function despite structural differences.

Example

In population genetics of bark beetles (Scolytinae), variation in isozymes of phosphoglucose isomerase helps distinguish cryptic species and track gene flow between geographically isolated populations.

Synonyms

• isoenzyme

Related Terms

• Allozyme
• enzyme polymorphism
• Electrophoresis
• metabolic regulation
• Genetic marker
• kinetics

Usage Notes

Isozyme refers to any structurally distinct enzyme form with identical catalytic activity, whether encoded by different loci or by multiple alleles at one locus; allozyme specifically denotes isozymes produced by allelic variants at a single locus. The term is sometimes used loosely in older literature for any enzyme variant detectable by electrophoresis. In arthropod studies, isozyme electrophoresis was historically central to measuring genetic diversity before DNA-based methods became standard.