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Enzyme Inhibition Calculator

Work out enzyme inhibition instantly with clear inputs, formula shown and shareable results.

About Enzyme Inhibition Calculator

Models competitive inhibition, where the apparent Km is multiplied by one plus the ratio of inhibitor concentration to Ki while Vmax is unchanged.

Formula

Competitive inhibition

alpha = 1 + [I]/Ki; v = Vmax[S] / (alpha x Km + [S]); Vmax is unaffected

Worked example

With the default values below, Enzyme Inhibition Calculator returns Velocity with inhibitor of 25.0000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Maximum velocityaccepts 0.001–100,000 micromol/min
100 micromol/min
Michaelis constantaccepts 0–1,000 mmol/L
5 mmol/L
Inhibitor concentration divided by Kiaccepts 0–200
5
Substrate concentrationaccepts 0–10,000 mmol/L
10 mmol/L

Results

Velocity with inhibitor
25.0000 micromol/min
Apparent Km
30.0000 mmol/L
Inhibition achieved
62.500%
Velocity without inhibitor
66.6667 micromol/min

Step by step

  1. 1Values used
  2. 2Competitive inhibition
  3. 3Velocity with inhibitor= 25.0000 micromol/min
  4. 4Apparent Km= 30.0000 mmol/L
  5. 5Inhibition achieved= 62.500
  6. 6Velocity without inhibitor= 66.6667 micromol/min

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How does non-competitive inhibition differ?

It lowers Vmax while leaving Km unchanged, because the inhibitor binds away from the active site.

Can competitive inhibition be overcome?

Yes, by raising substrate concentration, which is why competitive inhibitors lose effect at saturation.

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