Finding Michaelis-menten constant and Vmax

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In summary, the enzyme catalyzed reaction exhibited noncompetitive inhibition by the inhibitor, and the values of Km apparent and Vmax apparent can be calculated by extrapolating the data using a linear regression.
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babbagee
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Ok, here is the problem

A single-substrate enzyme catalyzed reaction was investigated in the presence of 1.0 mM inhibitor as well as in the absence of inhibitor, the intial substrate concentration being constant throughout. The following results were obtained:

----------------intial velocity (uM/min) that is micro Molar per min
(mM)--------=0------------ = 1.0mM
5.0-------------161-------------111
6.67------------194-------------141
10.00-----------263-------------183
20.00-----------400-------------279
50.00-----------576-------------399

Determine the type of inhibition exhibited by I and caluclate the values of Km apparent and Vmax apparent in the presence of 3.0mM inhibitor.

Ok i made a Linewaver-burk plot, and it looks seems that the inhibitor is a noncompetative inhibitor because it does not change Km but it does change Vmax, but the part i am having trouble with is how to calculate Km apparent and how to calculate Vmax apparent. Will that just be the Km apparent be just the x-intercept of the Lineweaver-burk plot, and Vmax apparent be the y-intercept of the second line where 1.0mM inhibitor was used. I am not sure though because it wants these values at 3.0mM. So can some one help me out please.

Thanks
 
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  • #2
for the help.Yes, the Km apparent would be the x-intercept of the Lineweaver-Burk plot and Vmax apparent would be the y-intercept of the line with 1.0mM inhibitor, but you will need to extrapolate the data to get the values at 3.0mM inhibitor. To do this, you can use a linear regression on the data points and then use the equation to calculate the values at 3.0mM.
 
  • #3
for sharing your results and question. Based on the data provided, it does appear that the inhibitor is exhibiting noncompetitive inhibition, as the inhibitor is affecting the Vmax but not the Km. To calculate the Km apparent and Vmax apparent at 3.0mM inhibitor, you can use the Lineweaver-Burk plot to extrapolate the values. The Km apparent can be calculated as the x-intercept of the extrapolated line, and the Vmax apparent can be calculated as the y-intercept of the line where 3.0mM inhibitor was used. However, it is important to note that these values may not be entirely accurate, as extrapolating from the data may introduce some error. It would be best to validate these values through further experimentation or by using a more accurate method such as nonlinear regression analysis.
 

1. What is Michaelis-Menten constant and Vmax?

Michaelis-Menten constant is a measure of the affinity between an enzyme and its substrate. It represents the substrate concentration at which half of the enzyme's active sites are occupied. Vmax, on the other hand, is the maximum rate of an enzyme-catalyzed reaction when the enzyme is saturated with substrate.

2. How do you determine the Michaelis-Menten constant and Vmax?

The Michaelis-Menten constant and Vmax can be determined by performing a series of experiments in which the initial reaction rate is measured at different substrate concentrations. These data points can then be plotted on a graph, and the values of Km and Vmax can be estimated using various mathematical models, such as the Lineweaver-Burk plot or the Michaelis-Menten equation.

3. What is the significance of Michaelis-Menten constant and Vmax in enzyme kinetics?

The Michaelis-Menten constant and Vmax are important parameters in enzyme kinetics as they provide information about the efficiency and rate of an enzyme-catalyzed reaction. They can also be used to compare the performance of different enzymes and to optimize reaction conditions for a specific enzyme.

4. What factors can affect the determination of Michaelis-Menten constant and Vmax?

The accuracy of the determination of Michaelis-Menten constant and Vmax can be affected by several factors, such as experimental errors, enzyme purity, substrate purity, and enzyme stability. In addition, the presence of enzyme inhibitors or other compounds that can interact with the enzyme can also affect the results.

5. Can Michaelis-Menten constant and Vmax be used for all enzymes?

No, the Michaelis-Menten constant and Vmax can only be determined for enzymes that follow the Michaelis-Menten kinetics, also known as simple enzyme kinetics. This type of kinetics assumes that the reaction is reversible and that the enzyme-substrate complex is in rapid equilibrium with the free enzyme and the free substrate. Enzymes that do not follow this type of kinetics, such as allosteric enzymes, cannot be characterized using Km and Vmax values.

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