1. What is Ki in Enzyme Kinetics?

The inhibition constant (Ki) represents the dissociation constant for the enzyme-inhibitor complex. It quantifies the potency of an enzyme inhibitor, with lower Ki values indicating stronger inhibition.

2. How Does the Calculator Work?

The calculator uses the Ki calculation formula:

Where:

• \( K_i \) — Inhibition constant (M)
• \( [I] \) — Inhibitor concentration (M)
• \( IC_{50} \) — Half-maximal inhibitory concentration (M)

Explanation: This formula converts IC50 values from dose-response curves to Ki values, providing a more fundamental measure of inhibitor potency.

3. Importance of Ki Calculation

Details: Ki values are essential for comparing inhibitor potencies, understanding enzyme mechanism, drug development, and determining the type of inhibition (competitive, non-competitive, uncompetitive).

4. Using the Calculator

Tips: Enter inhibitor concentration and IC50 value in molar units (M). Both values must be positive numbers. The calculator will compute the inhibition constant Ki.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between Ki and IC50?
A: Ki is a true dissociation constant, while IC50 depends on experimental conditions. Ki provides a more fundamental measure of inhibitor potency.

Q2: When should I use this Ki calculation?
A: Use this calculation when you have IC50 values from dose-response experiments and want to convert them to Ki values for better comparison between different inhibitors.

Q3: What are typical Ki values?
A: Ki values range from picomolar (pM) to millimolar (mM), with lower values indicating more potent inhibitors. Drug candidates typically have Ki values in nanomolar range.

Q4: Are there limitations to this calculation?
A: This calculation assumes certain conditions and may not be accurate for all types of inhibition. For precise determination, full enzyme kinetic analysis is recommended.

Q5: How does substrate concentration affect Ki?
A: For competitive inhibitors, Ki is independent of substrate concentration, while for other inhibition types, the relationship may be more complex.