Competitive inhibitor

Inhibitors that produce competitive inhibition

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competitiveness inhibitor Is competitive inhibition Inhibitor of. It usually has structural Similarity , can compete with the substrate for the binding site , resulting in enzymatic activity Reversible inhibitory effect. Another competitive inhibitor Chemical structure There is no similarity with the substrate in molecular shape, so it is not active center It binds to the enzyme, but outside the active center. However, once combined, the conformation of the enzyme will change, resulting in the inability of the active center to Recombine Substrate. Similarly, if the substrate first combines with the active center, it will lead to inhibitors Junction site As a result of the conformational change of, the inhibitor can no longer bind to the enzyme. Therefore, these competitive inhibitors and substrates are mutually exclusive in binding to enzymes.

The second competitive inhibitor and Non competitive inhibitor The difference is that non competitive inhibitors and substrates can combine with enzymes to form Ternary complex IES, while the former cannot.

Chinese name: Competitive inhibitor
Foreign name: Competitive inhibitor

Interpretation: produce Competitive inhibition Of inhibitor
Category: medicine

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conceptual analysis

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If the inhibitor concentration is constant, when the substrate concentration is low ([S]) inhibition The most obvious is that when [S] is increased, the inhibition will decrease. When [s] is increased to very strong, the inhibition will almost disappear, reaching the maximum without inhibitor reaction rate (V max ）The kinetic characteristics are: the apparent reaction constant (Km) increases, V max unchanged. The degree of inhibition is only related to the inhibitor concentration.

Typical examples are Malonic acid and Oxaloacetic acid yes Succinate dehydrogenase Inhibition of; Sulfonamides And P-aminobenzoic acid (Synthesis Dihydrofolate Inhibits bacterial dihydrofolate synthetase Etc.

structure characteristics

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① Substrate analogue For example, α- Glucosidase inhibitor as Acarbose (acarbose)、 Voglibose (voglibose) and Miglitol （Miglitol）

② Transition analogue as Benzoyl Alanine is Chymotrypsin Of transition state inhibitor 。

③ Of some compounds Plane structure It is not similar to the substrate, but three-dimensional conformation It is very similar and has become a competitive inhibitor. The action principle of some competitive inhibitors is that Enzyme active center Of metal ion Complexation, which hinders the entry of substrate, thus inhibiting enzymatic activity The purpose of.

Competitive inhibition^[1]

double-reciprocal plot

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The curve drawn by this equation and the values of each parameter are shown in Figure 1:

Figure 1 Competitive inhibitors

For more detailed analysis, please refer to Reciprocal equation And Michaelis constant Relevant data.

Competitive inhibitor

Competitive inhibition K i Solution method of

① Calculate the apparent Michaelis constant K from the double reciprocal graph m app And then substitute K m app =K m (1+[I]/K i ）K can be calculated i 。

② Obtain K at each I concentration from the double reciprocal graph m app The value pair corresponds to [I] and is then plotted from the intercept K can be measured directly m , K can be directly measured from its cross section i 。

③ A cluster made from different fixed [I] The slope of the line 1/S for corresponding [I] reproduction graph, its longitudinal intercept is K m /V max , slope K m /V max K i , the cross section is - K i 。

Competitive inhibitor

④Dixon Graphing method Find K i value

Competitive inhibitor

Calculation formula

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First view about IC50 Definition of. Its value depends on the concentration of enzyme and substrate used in the experiment. When the concentration of enzyme is fixed, IC50 value and K i 、K m And competitive inhibitors

Competitive inhibitor

The substrate concentration [S] shows the following relationship:

According to this equation, when the substrate concentration is greater than K m IC50 value is higher than K i Value, especially when the substrate concentration is high, K i The lower value is more obvious.

Competitive inhibitor Michaelis equation It can also be written as v=V max [S]/(K m (1+[I]/K i )+[S])

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