Enzyme Kinetics Calculator
μM/min
mM
mM
Initial Reaction Velocity ($V_0$)
0.000
μM/min
Understanding Enzyme Reaction Rate
This calculator determines the initial reaction velocity ($V_0$) of an enzymatic reaction based on the Michaelis-Menten kinetics model. This model is fundamental in biochemistry for describing the rate of enzymatic reactions by relating reaction rate to substrate concentration.
$$V_0 = \frac{V_{max} \cdot [S]}{K_m + [S]}$$
Key Parameters
- $V_0$ (Initial Velocity): The rate of the reaction at a specific substrate concentration, typically measured in $\mu M/min$ or $\mu mol/min$.
- $V_{max}$ (Maximum Velocity): The maximum theoretical rate the reaction can achieve when the enzyme is fully saturated with substrate. At this point, adding more substrate does not increase the rate.
- [$S$] (Substrate Concentration): The amount of substrate available for the enzyme to act upon, usually measured in molarity ($mM$ or $\mu M$).
- $K_m$ (Michaelis Constant): The substrate concentration at which the reaction rate is exactly half of $V_{max}$. It is an inverse measure of the enzyme's affinity for the substrate (a lower $K_m$ indicates higher affinity).
How to Calculate Enzyme Kinetics
To perform the calculation manually using the Michaelis-Menten equation, follow these steps:
- Identify the maximum velocity ($V_{max}$) of the enzyme system.
- Measure or select the current substrate concentration ([$S$]).
- Determine the Michaelis constant ($K_m$) for the specific enzyme-substrate pair.
- Add the substrate concentration to the Michaelis constant ($K_m + [S]$).
- Multiply $V_{max}$ by the substrate concentration ($V_{max} \times [S]$).
- Divide the result from step 5 by the result from step 4.
Example Calculation
Let's assume we are studying the enzyme catalase:
- $V_{max}$: 200 $\mu M/min$
- $K_m$: 4.0 $mM$
- Substrate Concentration [$S$]: 6.0 $mM$
Plugging these values into the formula:
$V_0 = \frac{200 \times 6.0}{4.0 + 6.0}$
$V_0 = \frac{1200}{10.0}$
$V_0 = 120 \mu M/min$
In this example, because the substrate concentration ($6.0$) is higher than the $K_m$ ($4.0$), the reaction velocity is more than half of $V_{max}$.
Why is $V_{max}$ and $K_m$ Important?
Understanding these constants helps researchers determine the efficiency of an enzyme. $V_{max}$ is dependent on the total amount of enzyme present, while $K_m$ is an intrinsic property of the enzyme itself regarding a specific substrate. This data is crucial in pharmacology for drug design, specifically in understanding enzyme inhibition.