Inhibitor's Dissociation Constant Given Michaelis Menten Constant Calculator

Formula Used:

\[ K_i = \frac{I}{\left(\frac{K_{mapp}}{K_M} - 1\right)} \]

Inhibitor Concentration (I):

mol/m³

Apparent Michaelis Constant (K_mapp):

mol/m³

Michaelis Constant (K_M):

mol/m³

Enzyme Inhibitor Dissociation Constant (K_i):

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1. What is the Inhibitor's Dissociation Constant?

The Enzyme Inhibitor Dissociation Constant (K_i) is a measure of the affinity between an enzyme and its inhibitor. It represents the concentration of inhibitor required to occupy half of the enzyme's active sites and is measured by titrating inhibitor into an enzyme solution while monitoring heat changes.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ K_i = \frac{I}{\left(\frac{K_{mapp}}{K_M} - 1\right)} \]

Where:

\( K_i \) — Enzyme Inhibitor Dissociation Constant (mol/m³)
\( I \) — Inhibitor Concentration (mol/m³)
\( K_{mapp} \) — Apparent Michaelis Constant (mol/m³)
\( K_M \) — Michaelis Constant (mol/m³)

Explanation: This formula calculates the dissociation constant for competitive inhibitors by comparing the apparent Michaelis constant in the presence of inhibitor with the true Michaelis constant.

3. Importance of Dissociation Constant Calculation

Details: The dissociation constant is crucial for understanding enzyme-inhibitor interactions, determining inhibitor potency, and designing effective enzyme inhibitors for therapeutic applications.

4. Using the Calculator

Tips: Enter inhibitor concentration, apparent Michaelis constant, and Michaelis constant in mol/m³. All values must be positive, and K_mapp must be greater than K_M for a valid result.

5. Frequently Asked Questions (FAQ)

Q1: What does a lower K_i value indicate?
A: A lower K_i value indicates stronger inhibitor binding and higher affinity between the enzyme and inhibitor.

Q2: When is this formula applicable?
A: This formula is specifically for competitive inhibitors where the inhibitor binds to the enzyme's active site.

Q3: What are typical units for K_i?
A: K_i is typically expressed in concentration units such as mol/m³, M (molar), or mM (millimolar).

Q4: How does K_i relate to IC₅₀?
A: For competitive inhibitors, K_i can be calculated from IC₅₀ using the Cheng-Prusoff equation when substrate concentration and K_M are known.

Q5: What factors can affect K_i measurements?
A: Temperature, pH, ionic strength, and the presence of other molecules can influence K_i values and should be controlled during measurements.