Enzyme Activity & Specific Activity Calculator

Calculate enzyme activity (U) and specific activity (U/mg) from absorbance, volume, and more.

Enter your experimental data to determine enzyme activity and, if desired, specific activity. All calculations are based on standard enzyme kinetics formulas.

Examples

See how to calculate enzyme activity with real-world data.

Standard Enzyme Activity Calculation

Standard

Calculate enzyme activity from absorbance change, total volume, extinction coefficient, path length, enzyme volume, and time.

ΔA (Change in Absorbance): 0.25

Total Volume (mL): 3 mL

Extinction Coefficient (M⁻¹cm⁻¹): 6220 M⁻¹cm⁻¹

Path Length (cm): 1 cm

Enzyme Volume (mL): 0.1 mL

Time (min): 5 min

Specific Activity Calculation

Specific

Calculate both enzyme activity and specific activity with protein amount provided.

ΔA (Change in Absorbance): 0.18

Total Volume (mL): 2.5 mL

Extinction Coefficient (M⁻¹cm⁻¹): 5400 M⁻¹cm⁻¹

Path Length (cm): 1 cm

Enzyme Volume (mL): 0.08 mL

Time (min): 4 min

Protein Amount (mg): 0.4 mg

High Enzyme Activity Example

High Activity

A case with high absorbance change and short reaction time.

ΔA (Change in Absorbance): 0.45

Total Volume (mL): 4 mL

Extinction Coefficient (M⁻¹cm⁻¹): 7000 M⁻¹cm⁻¹

Path Length (cm): 1 cm

Enzyme Volume (mL): 0.12 mL

Time (min): 2 min

Low Enzyme Activity Example

Low Activity

A case with low absorbance change and longer reaction time.

ΔA (Change in Absorbance): 0.05

Total Volume (mL): 3.5 mL

Extinction Coefficient (M⁻¹cm⁻¹): 6000 M⁻¹cm⁻¹

Path Length (cm): 1 cm

Enzyme Volume (mL): 0.1 mL

Time (min): 10 min

Other Titles
Understanding Enzyme Activity & Specific Activity: A Comprehensive Guide
Master the principles, calculations, and applications of enzyme activity in biochemistry.

What is Enzyme Activity?

  • Definition and Units
  • Why Measure Enzyme Activity?
  • Enzyme Activity vs. Specific Activity
Enzyme activity quantifies the catalytic ability of an enzyme to convert substrate into product per unit time. It is typically expressed in units (U), where one unit is the amount of enzyme that catalyzes the conversion of 1 micromole of substrate per minute under specified conditions.
Enzyme Activity Units

Examples of Enzyme Activity

  • If an enzyme converts 2 μmol of substrate in 1 minute, its activity is 2 U.
  • Specific activity is calculated by dividing enzyme activity by the amount of protein (U/mg).

Step-by-Step Guide to Using the Calculator

  • Input Data Collection
  • Calculation Process
  • Interpreting Results
To use the calculator, gather your experimental data: change in absorbance, total reaction volume, extinction coefficient, path length, enzyme volume, reaction time, and optionally protein amount. Enter these values into the calculator fields.
Calculation Steps

Step-by-Step Examples

  • Input ΔA = 0.25, V_total = 3.0 mL, ε = 6220 M⁻¹cm⁻¹, d = 1.0 cm, V_enzyme = 0.1 mL, t = 5 min.
  • The calculator computes enzyme activity and, if protein amount is provided, specific activity.

Real-World Applications of Enzyme Activity Measurement

  • Clinical Diagnostics
  • Pharmaceutical Research
  • Biotechnology and Quality Control
Enzyme activity measurements are essential in clinical diagnostics (e.g., liver function tests), pharmaceutical R&D (e.g., drug screening), and biotechnology (e.g., enzyme production quality control).
Applications in Science and Industry

Application Examples

  • Measuring ALT/AST activity in blood for liver health.
  • Assessing enzyme purity during protein purification.

Common Misconceptions and Correct Methods

  • Misinterpreting Absorbance Data
  • Ignoring Path Length
  • Incorrect Unit Conversions
Common mistakes include using incorrect extinction coefficients, neglecting to adjust for path length, or failing to convert units properly. Always ensure your data matches the required units and conditions.
Avoiding Calculation Errors

Misconception Examples

  • Using ε in L/(mol·cm) but entering volume in μL instead of mL.
  • Forgetting to divide by protein amount for specific activity.

Mathematical Derivation and Examples

  • The Enzyme Activity Formula
  • Specific Activity Calculation
  • Worked Example Calculations
The standard formula for enzyme activity is: Activity (U) = (ΔA × Vtotal) / (ε × d × Venzyme × t). Specific activity is Activity (U) divided by protein amount (mg).
Example Calculation

Mathematical Examples

  • Given ΔA = 0.25, V_total = 3.0 mL, ε = 6220 M⁻¹cm⁻¹, d = 1.0 cm, V_enzyme = 0.1 mL, t = 5 min: Activity = (0.25 × 3.0) / (6220 × 1.0 × 0.1 × 5) = 0.0024 U.
  • If protein amount = 0.5 mg, Specific Activity = 0.0024 U / 0.5 mg = 0.0048 U/mg.