Enzyme activity is the catalytic effect exerted by an enzyme.

Enzyme activity = moles converted per unit time = rate × reaction volume Enzyme activity is a measure of quantity of enzyme present. The SI unit is the katal, 1 katal = 1 mol s-1, but this is an excessively large unit. A more practical value is 1 enzyme unit (EU) = 1 μmol min-1 (μ = micro, x 10-6).

Measurement

• Specific activity is expressed as enzyme units per milligram of enzyme
• Molecular activity is expressed as molecules of substrate transformed per minute per molecule of enzyme. It is the amount of enzyme that will catalyze the transformation of one micromole of substrate per minute under standard conditions of temperature, pH and optimal substrate concentration.