Enzyme-specific activity is a measure of enzyme purity, reflecting the amount of enzyme activity per milligram of total protein. It quantifies the catalytic efficiency of an enzyme preparation. A higher specific activity indicates a purer enzyme sample, as a greater proportion of the total protein contributes to the desired enzymatic reaction. For instance, an enzyme preparation with a specific activity of 10 U/mg has twice the activity per unit of protein compared to a preparation with 5 U/mg.
Determining specific activity is crucial in enzyme purification and characterization. As purification steps are performed, the specific activity should increase, indicating the removal of contaminating proteins. Monitoring this parameter provides a valuable assessment of the effectiveness of each purification stage. Furthermore, specific activity facilitates comparisons of enzyme preparations obtained through different isolation or expression methods. Historically, the concept evolved as a means to standardize and compare enzymatic activities across various laboratories and experimental conditions.
