Michaelis Menten pure inhibition comparison calculator

What this calculation answers

An inhibitor can alter an initial-rate curve in different ways depending on the stated kinetic model. The same inhibitor concentration does not imply the same apparent maximum rate or apparent Km across competitive, pure noncompetitive and uncompetitive cases.

This page compares the selected ideal inhibition curve with the uninhibited Michaelis–Menten curve. It evaluates entered parameters rather than inferring a mechanism from experimental measurements.

The Integrated reaction order fit calculator fits integrated concentration-time kinetics. The present page instead predicts initial rates from supplied enzyme and pure-inhibition parameters.

Use the right input conventions

Use one concentration unit for substrate, Km, inhibitor and Ki. Maximum rate uses a separately chosen consistent rate unit, such as micromoles per minute. Ki and Km must be positive, while zero substrate or inhibitor is permitted.

Competitive inhibition applies the concentration factor to Km; pure noncompetitive applies it to both denominator terms; uncompetitive applies it only to the substrate term. The pure noncompetitive restriction is deliberate.

Interpret the result

The main rate is evaluated at the entered substrate concentration. Apparent maximum rate and apparent Km summarize how the selected denominator can be written in standard Michaelis–Menten form.

The plotted curves show model initial rates over a substrate range based on entered Km. They are not time-course predictions, and their displayed agreement or separation does not establish which mechanism a real inhibitor follows.

Work through the example

With Vmax one hundred, Km ten, substrate ten, inhibitor ten and Ki ten, the factor is two. Competitive rate is one hundred divided by three, while pure noncompetitive rate is twenty-five.

At these same values uncompetitive rate is also one hundred divided by three, despite its different curve and apparent parameters. Equal rates at one substrate point therefore cannot identify a mechanism.

Where the model stops

Substrate depletion, enzyme inactivation and time-dependent binding are not modeled. Mixed inhibition with unequal binding constants needs two distinct factors and is excluded rather than silently approximated.

No kinetic parameter fitting or pharmacological recommendation is supplied. Experimental mechanism assessment requires appropriate measurements, controls and a model suited to the assay rather than one illustrative curve.