Question

For enzymes that follow Michaelis–Menten kinetics, the inhibitors that inhibit enzyme activity include reversible inhibitor and irreversible inhibitor.
1. Describe the type of reversible inhibitor.
2. Suggest ways to distinguish between types of inhibitors through enzyme reaction experiments.

Answer 1

1. Reversible inhibitors can bind to enzymes through weak non-covalent interactions such as ionic bonds, hydrophobic reactions, and hydrogen bonds. Because reversible inhibitors do not form any chemical bonds or reactions with the enzyme , they are formed rapidly and can be easily removed, thus the enzyme and inhibitor complex is rapidly dissociated in contrast to irreversible inhibition.

There are three types of reversible inhibitors, they are:-

1. Competitive inhibition - Raises Km only. As the name suggests , compete with substrates to bind to the enzyme at the same time. The inhibitor has an affinity for the active site of an enzyme where the substrate also binds to. Competitive inhibitors are often similar in structure to the real substrate. So 1/V= 1/Vmax+ alpha-Km/Vmax+1/(S​)0

2. Uncompetitive inhibition- Lowers Vmax and Km. Uncompetitive inhibitors bind to the enzyme at the same time as the enzymes substrates. However, the binding of the affects the binding of the substrate, and vice-versa. The binding to the allosteric site changes the confirmation of the enzyme so that the affinity of the substrate for the active site is reduced. So 1/V= alpha'/Vmax+ (Km/Vmax)1/(S)0

3. Non-competitive inhibition- Lowers Vmax only. Non-competitive inhibitors bind to the other sites(Allosteric sites), not the active site, and stops the enzymes activity by changing the shape of the active site. Therefore , concentration of the substrate is meaningless unlike in competitive inhibition. So here alpha greater than 1 and alpha' greater than 1 so, K​​​​​​1​​​= K​​​​​​K1​​​​ '. And alpha=alpha'.

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