Here, we talk about the enzyme inhibition and reaction rate of enzymes. As we all know the enzymes are mainly proteins and they play a very important role in the living organism (i.e. the plants, animals as well as bacteria). The main function of the enzymes in the living organism is to catalyze the biochemical reaction that occurs within the cells of the living things to keep them alive.
Enzyme Inhibition and Reaction Rate of Enzyme
Enzyme Inhibition and Reaction Rate of Enzyme is an essential topic in biochemistry. First, we should know the classification of the inhibition of the enzyme.
There are two kinds of enzyme inhibition. They are-
- Reversible Inhibition and
- Irreversible Inhibition.
Now the Reversible inhibition can further be classified. There are three kinds of Reversible Inhibition —
- Competitive Inhibition,
- Uncompetitive Inhibition, and
- Non-competitive Inhibition.
You can read the article to learn the enzyme inhibitors and the classification of enzyme inhibitions
Today we will discuss only Competitive Inhibition. So let’s start it now.
Competitive Inhibition: The inhibitor binds only to Enzymes and inhibits the Enzymes to function is known as Competitive Inhibition. A competitive inhibitor is reversible and has a structure to fit the active site of the enzyme. So the inhibitors compete with the substrate to bind with the enzyme. Once it fit with the active site of an Enzyme it makes an Enzyme-Inhibitor complex, the substrate can’t bind with the enzyme. But it is a reversible process.
Competitive inhibition can be reversed by increasing substrate concentration
The competitive inhibition can be reversed by increasing the concentration of the substrate. As the concentration of the substrate is increasing the number of substrate molecules increasing as well around the active site of the Enzyme that is catalyzing a biochemical reaction. So the Inhibitor molecules are released from the active site of the Enzyme as well as can’t bind to the active site of the enzyme as often as before. Then the substrate molecules can bind again to the active site of the Enzyme.
In the presence of a competitive inhibitor, Michaelis-Menten equation-
The Michaelis-Menten equation will be changed a little bit for this enzyme inhibition process. Let’s see what changes will take place in the equation.
This is the Lineweaver-Burk equation in the presence of a competitive inhibitor. In the competitive inhibition, the value of Km changes while Vmax does not.
- Effect on Vmax: Increasing substrate concentration [S] reverses the impact of a competitive inhibitor. The reaction velocity reaches the Vmax observed in the absence of inhibitors at a sufficiently elevated concentration of the substrate.
Effect on Km: For a specified substrate, a competitive inhibitor rises the value of km. This means that more substrate is needed in the presence of a competitive inhibitor to achieve 1⁄2Vmax.
- Effect on the Lineweaver-Burk plot: Competitive inhibition shows a characteristic Lineweaver-Burk plot in which the plots of the inhibited and uninhibited reactions intersect on the y-axis at 1/Vmax (Vmax is unchanged), and show different x-axis intercepts, indicating that the apparent Km is increased in the presence of the competitive inhibitor.
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