Initial Reaction Rate Formula:
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Definition: This calculator determines the initial reaction rate (V0) of an enzyme-catalyzed reaction when substrate concentration is much lower than the Michaelis constant (S ≪ KM).
Purpose: It helps biochemists and enzymologists understand reaction kinetics under conditions where the reaction rate is directly proportional to substrate concentration.
The calculator uses the formula:
Where:
Explanation: The formula represents the first-order region of Michaelis-Menten kinetics where reaction rate is linearly dependent on substrate concentration.
Details: Calculating initial rates helps determine enzyme efficiency, compare different enzymes, and understand metabolic pathway regulation.
Tips: Enter the catalytic rate constant, initial enzyme concentration, substrate concentration, and Michaelis constant. All values must be > 0.
Q1: When is this equation valid?
A: Only when substrate concentration is much lower than KM (typically S < 0.1×KM).
Q2: What does kcat represent?
A: The turnover number - how many substrate molecules one enzyme site converts to product per second.
Q3: How do I determine KM experimentally?
A: Through a series of initial rate measurements at different substrate concentrations and nonlinear regression.
Q4: What units should I use?
A: Consistent molar units (mol/m3 = mM) and time in seconds.
Q5: Can I use this for inhibitor studies?
A: Only for competitive inhibitors where the apparent KM changes but kcat remains constant.