1. What is Catalytic Rate Constant?

Definition: The Catalytic Rate Constant (k_cat) is the rate constant for conversion of the enzyme-substrate complex to enzyme and product.

Purpose: It measures the turnover number of an enzyme, indicating how many substrate molecules one enzyme molecule can convert to product per second.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( k_{cat} \) — Catalytic rate constant (s⁻¹)
• \( V_0 \) — Initial reaction rate (mol/m³·s)
• \( K_D \) — Dissociation rate constant (mol/m³)
• \( S \) — Substrate concentration (mol/m³)
• \( [E_0] \) — Initial enzyme concentration (mol/m³)

Explanation: The formula relates the initial reaction rate to enzyme and substrate concentrations, accounting for enzyme-substrate dissociation.

3. Importance of Catalytic Rate Constant

Details: k_cat is crucial for understanding enzyme efficiency, comparing different enzymes, and predicting reaction rates under various conditions.

4. Using the Calculator

Tips: Enter all required values in appropriate units. Ensure substrate and enzyme concentrations are positive values.

5. Frequently Asked Questions (FAQ)

Q1: What does a high k_cat value indicate?
A: A high k_cat means the enzyme is very efficient, converting many substrate molecules per second.

Q2: How is k_cat related to enzyme efficiency?
A: k_cat is part of the catalytic efficiency measure (k_cat/K_M), where higher values indicate more efficient enzymes.

Q3: What are typical k_cat values?
A: Most enzymes have k_cat values between 1 and 10⁶ s⁻¹, with very efficient enzymes at the higher end.

Q4: Can k_cat exceed 10⁶ s⁻¹?
A: Extremely rare, as this approaches the diffusion limit of molecular encounters in solution.

Q5: How does temperature affect k_cat?
A: Like most rate constants, k_cat typically increases with temperature up to the enzyme's denaturation point.