Why does mM x mL equal umol?

1 mM is 1 umol/mL, so multiplying by mL gives umol.

When should I use dilution factor?

Use it when the enzyme sample was diluted before adding it to the assay.

Enzyme Activity Calculator

Calculate enzyme units, stock activity, and specific activity from assay measurements.

Answer

Stock activity

Enzyme activity: 0.08 U

Specific activity: 8 U/mg

Product formed: 0.24 umol

Protein in assay: 0.01 mg

Product concentration (mM)Reaction volume (mL)Reaction time (min)Enzyme volume added (mL)Enzyme dilution factorOriginal enzyme stock protein concentration (mg/mL)

mM x mL gives umol product. Protein concentration is the original enzyme stock concentration; dilution factor converts stock concentration to the diluted enzyme added to the assay.

Examples

Activity details

Product formed	Enzyme activity	Activity per reaction mL	Specific activity	Stock protein concentration
0.24 umol	0.08 U	0.08 U/mL	8 U/mg	2 mg/mL

Formula

U = umol product / min; U/mL stock = U x dilution / enzyme volume

Specific activity is stock activity divided by the original enzyme stock protein concentration.

Symbol	Variable	Description
U	Enzyme unit	One umol of product formed per minute.
Dilution	Dilution factor	Correction back to the original enzyme stock.
mg/mL	Protein concentration	Used to calculate U per mg protein.

How to use it

1
Enter assay product
Use product concentration in mM and reaction volume in mL.
2
Enter enzyme amount
Use the diluted enzyme volume added to the assay, the dilution factor from stock, and the original stock protein concentration.
3
Read activity
The top result shows stock activity in U/mL.

Result fields

These outputs match common enzyme assay reporting.

Result	Meaning
U	umol product per minute in the assay
U/mL	Activity normalized to enzyme stock volume
U/mg	Activity normalized to protein amount

Enzyme activity FAQ

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