Enzyme Activity Calculator

Your details

Spectrophotometric assays use absorbance change; product assays measure product directly.
Change in absorbance per minute from a continuous assay at your wavelength.
Molar extinction coefficient of the product (or consumed substrate) at your wavelength. NADH at 340 nm: 6.22 mM⁻¹·cm⁻¹.
mM⁻¹·cm⁻¹
Optical path length of the cuvette, typically 1 cm for standard cuvettes.
cm
Total volume in the cuvette or reaction vessel.
mL
How many times the enzyme extract was diluted before the assay (1 = no dilution). Multiplies the activity to give the activity in the undiluted sample.
Mass of total protein in the assay. Leave at 0 to skip specific activity.
mg
Reaction rateVery low purity
0.0193μmol/min

Micromoles of product formed per minute under assay conditions

Enzyme activity0.0193U
Specific activity0.3859U/mg
Volumetric activity0.0193U/mL
Rate (nmol/min)19.29nmol/min
Rate (μmol/min)0.0193
Activity (U)0.0193

Reaction rate: 0.0193 μmol/min

  • Your enzyme converts 0.0193 μmol of substrate per minute under these assay conditions.
  • The enzyme activity is 0.0193 U (micromoles of product per minute).
  • Specific activity is 0.39 U/mg protein, which is very low - consistent with a whole-cell lysate or crude homogenate.
  • Spectrophotometric assays assume linear absorbance change. Verify the reaction is in the linear range (ΔA typically below 0.05/min for reliable Beer-Lambert linearity).

Next stepTo track purification fold, run the same assay on your next fraction and divide the new specific activity by the crude extract value.

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