Enzyme Inhibition and Reaction Rate of Enzyme
Enzyme Inhibition and Reaction Rate of Enzyme is a important topic in the biochemistry. We use the study in many ways. first we should know the classification of the Enzyme.
There are two kinds of enzyme inhibition-
- Reversible Inhibition and
- Irreversible Inhibition.
Again there are three kinds of Reversible Inhibition —
- Competitive Inhibition
- Uncompetitive Inhibition and
- Non competitive Inhibition.
Today we will discuss about only Competitive Inhibition.
Competitive Inhibition: Inhibitor (I) binds only to Enzymes (E), but not to the enzyme-Substrate complex (ES) and inhibits the Enzymes (E) to function is known as the Competitive Inhibition. It is a real kind of Inhibition. It really happens in real for an Enzyme. A competitive inhibitor is reversible and has a structure like the substrate to fit to the active site of the enzyme. So Competitive competes with the substrate for the active site of the enzymes. Once It fit with the active site of an Enzyme it makes an Enzyme-Inhibitor complex (EI), the Substrate can’t bind with the Enzyme. So the Inhibition takes place. But it is reversible process so the Enzyme-Inhibitor complex (EI) breaks down and again enzyme become functional.
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 molecule increasing around the active site of the Enzymes. So the Inhibitor molecules are released from the active site of the Enzyme. Then the Substrate molecules can bind again to the active site of the Enzyme.
In the presence of a competitive inhibitor, Michaelis-Menten equation–
this is 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: The effect of a competitive inhibitor is reversed by increasing Substrate concentration [S]. At a sufficiently high substrate concentration, the reaction velocity reaches the Vmax observed in the absence of inhibitors.
Effect on Km: A competitive inhibitor increases the apparent Km for a given substrate. This means that, in the presence of a competitive inhibitor, more substrate is needed 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.