1. What is Catalytic Rate Constant?

Definition: The catalytic rate constant (k_cat) represents the number of substrate molecules converted to product per enzyme molecule per second when the enzyme is saturated with substrate.

Purpose: It measures the enzyme's maximum catalytic efficiency under saturating substrate conditions.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( k_{cat} \) — Catalytic rate constant (s⁻¹)
• \( V_{max} \) — Maximum reaction rate (mol/m³·s)
• \( [E_0] \) — Initial enzyme concentration (mol/m³)

Explanation: The formula calculates how many reactions each enzyme molecule can catalyze per second when fully saturated with substrate.

3. Importance of Catalytic Rate Constant

Details: k_cat is a fundamental parameter in enzyme kinetics that helps compare enzyme efficiencies and understand catalytic mechanisms.

4. Using the Calculator

Tips: Enter V_max in mol/m³·s and [E₀] in mol/m³. Both values must be > 0. The calculator assumes substrate concentration is much higher than K_M.

5. Frequently Asked Questions (FAQ)

Q1: What does a higher k_cat value mean?
A: A higher k_cat indicates a more efficient enzyme that can process more substrate molecules per second.

Q2: How is k_cat different from K_M?
A: While k_cat measures catalytic efficiency at saturation, K_M reflects the substrate concentration needed for half-maximal velocity.

Q3: What are typical k_cat values?
A: k_cat values range from <1 s⁻¹ for slow enzymes to >10⁶ s⁻¹ for very efficient enzymes.

Q4: How does temperature affect k_cat?
A: k_cat generally increases with temperature until the enzyme denatures.

Q5: Can k_cat be greater than diffusion limits?
A: No, k_cat cannot exceed the rate at which substrate can diffuse to the enzyme's active site (~10⁸-10⁹ M⁻¹s⁻¹).