measurement
Last reviewed 01/2018
Standardly, the activity of an enzyme is measured by the rate of product formation per minute. Typically, this is measured at a time when the rate of reaction is linear - the amount of product is increasing by a constant amount per unit time. However, the reaction must be optimized according to:
- substrate concentration
- coenzyme concentration
- buffer type
- buffer concentration
- pH
- temperature
Individual laboratories have their own criteria and it is best to interpret values in the light of local normal ranges. Activity is expressed in International Units per litre (IU/l). This is the amount of enzyme which metabolises 1 micromole of substrate per minute.
The concentration of enzyme protein, as opposed to its activity, is occasionally measured.