Enzyme Reaction Rate Calculator
Please enter valid positive numbers for all fields.
The maximum reaction rate at saturating substrate concentration (units: μM/min, etc.)
The concentration of the substrate available (units: mM, μM, etc.)
Substrate concentration at which reaction rate is half of Vmax
Calculated Initial Velocity (v0)
0
rate units (matches Vmax units)
Equation Used: v = (Vmax × [S]) / (Km + [S])
About Enzyme Kinetics and Reaction Rates
This Enzyme Reaction Rate Calculator utilizes the Michaelis-Menten equation to determine the initial velocity (rate) of an enzymatic reaction. By inputting the maximum possible velocity (Vmax), the substrate concentration ([S]), and the Michaelis constant (Km), researchers and students can predict how fast an enzyme will process a substrate under specific conditions.
The Michaelis-Menten Equation
The standard model for enzyme kinetics is defined by the following formula:
v = (Vmax × [S]) / (Km + [S])
Where:
- v (Velocity): The initial rate of the reaction.
- Vmax: The maximum rate achieved by the system, happening at saturating substrate concentrations.
- [S]: The concentration of the substrate.
- Km (Michaelis Constant): The substrate concentration at which the reaction rate is exactly half of Vmax. It is an inverse measure of the enzyme's affinity for the substrate.
What do the Parameters Mean?
Understanding these parameters is crucial for biochemistry and pharmacology:
- High Vmax: Indicates a high turnover number; the enzyme can convert a lot of substrate into product per unit of time once saturated.
- Low Km: Indicates high affinity. The enzyme requires only a small amount of substrate to reach 50% of its maximum speed.
- High Km: Indicates low affinity. The enzyme requires a high concentration of substrate to function efficiently.
Example Calculation
Suppose you are studying an enzyme with a maximum velocity (Vmax) of 100 μM/min. The Michaelis constant (Km) is determined to be 4 mM. You want to know the reaction rate when the substrate concentration ([S]) is 2 mM.
Using the formula:
v = (100 × 2) / (4 + 2)
v = 200 / 6
v ≈ 33.33 μM/min
In this scenario, because the substrate concentration (2 mM) is lower than the Km (4 mM), the enzyme is operating at less than half its maximum capacity.
Factors Affecting Reaction Rate
While this calculator focuses on substrate concentration, remember that other physical factors influence enzyme activity:
- Temperature: Reaction rates generally increase with temperature until the enzyme denatures.
- pH: Enzymes have an optimal pH range; deviations can reduce activity or denature the protein.
- Inhibitors: Competitive, non-competitive, and uncompetitive inhibitors will alter effective Km and Vmax values.