Enzyme Specific Activity
Calculator
Results
- Specific activity (U/mg)
- 55.555555
- Total enzyme units (U)
- 250
- Specific activity (nkat/mg)
- 925.925925
Biology and lab results
| Specific activity (U/mg) | 55.555555 |
| Total enzyme units (U) | 250 |
| Specific activity (nkat/mg) | 925.925925 |
formula-map diagram
- Specific activity (U/mg)
- 55.555555
- Total enzyme units (U)
- 250
- Specific activity (nkat/mg)
- 925.925925
Formula breakdown
Formula
specific activity = total units ÷ total protein (mg)= 55.555555555556
Note
Simplified model: these results use standard textbook laboratory relationships and average constants (A260 = 1 for 50 µg/mL dsDNA, 617.96 g/mol per base pair, ~110 Da per amino acid, ideal exponential growth). Real samples vary with purity, contaminants, buffer, temperature and instrument calibration. Always confirm against your own standards and protocol; do not use for diagnostic or safety-critical work.
More in Biology and lab
See all →Frequently asked questions
What does specific activity measure, and why is it more useful than total activity alone?+
Specific activity is enzyme activity per unit mass of total protein (typically units per milligram), which normalizes for how much of the sample is actually the enzyme of interest versus other proteins, making it possible to compare enzyme purity and to track purification progress across steps.
What is the formula the calculator uses?+
Specific activity = total enzyme activity (in units) divided by total protein mass (in mg), where one unit is usually defined as the amount of enzyme converting one micromole of substrate per minute under specified assay conditions.
How do I know if my purification step actually improved enzyme purity?+
Compare specific activity before and after the step: if specific activity increases, you have enriched the enzyme relative to contaminating protein, even if total activity (units) dropped somewhat due to normal losses during purification.
What is the difference between specific activity and specific activity 'fold purification'?+
Fold purification is the ratio of specific activity after a step to the specific activity of the starting material, showing relative enrichment across a purification scheme, whereas specific activity itself is an absolute value at one particular stage.
Why would specific activity decrease even though the enzyme was successfully purified?+
If the enzyme loses activity due to denaturation, degradation, or loss of a required cofactor during the purification step, specific activity can drop even as contaminating protein is removed, so specific activity reflects functional yield, not just how much target protein is present.