The action of a competitive inhibitor to that of a non-competitive enzyme inhibitor - Essay Example

COMPARE AND CONTRAST THE ACTION OF A COMPETITIVE INHIBITOR TO THAT OF A NON-COMPETITIVEENZYME INHIBITOR Institute Compareand contrast the action of a competitive inhibitor to that of a non-competitive enzyme inhibitor A substance which is used to catalyze the chemical reactions is called an enzyme. Enzymes are thermolabile, colloidal and protein in nature. Enzymes lower the activation energy of the chemical reactions and thus accelerate the chemical reactions, for example oxidoreductases, transferases and hydrolases etc.

On the other hand an inhibitor is a substance which binds to the enzyme and lowers the activity of enzyme. Inhibitors are of two types reversible or irreversible. Reversible inhibitors are those which bind to the enzyme and cause inhibition but do not change the chemical structure of the enzyme. Irreversible inhibitors are those which bind to the enzyme and change the chemical structure of the enzyme thus making them unable to perform its function accurately. Many drugs are enzyme inhibitors (Chatterjea et al 2007; Murray 2009).

The mechanism of enzymatic reactions is proposed by Michaelis and Menten in their hypothesis. Their hypothesis states that the enzyme molecule (E) combines to the substrate molecule (S) and form an enzyme-substrate complex (ES) which then further dissociate to form product (P) and enzyme (E). The enzyme which is dissociated from this reaction in its original form is the one that is used in this reaction because enzyme is not used up itself but it only accelerates the reaction. And the dissociated enzyme is now ready for another reaction to combine and perform its function.

There is a specific site on the enzyme to which a substrate can bind and that site is known as active site or catalytic site. The active site is made in a manner which provides a three dimensional cleft or fissure for the substrate. The three dimensional cleft is formed by the folding of secondary and tertiary structures of the amino acids in the enzyme. A model for the enzyme-substrate complex was proposed by Koshland which is known as Induced-fit Model. This model states that the substrate makes conformational changes in the active site while binding to the active site to achieve the ultimate shape of the enzyme-substrate complex.

According to this model the active site is not an inflexible and preformed structure (Chatterjea et al 2007; Murray 2009; Vasudevan et al 2005). When an inhibitor combines to the active site of enzyme it forms enzyme-inhibitor complex and the enzyme is not capable of dissociating the inhibitors to the products thus stopping the action of enzyme. Competitive inhibitors are those compounds which have same structure to the substrate and compete for the active site with the substrate and thus bind to the active site of the enzyme and for m the enzyme-inhibitor complex.

In this complex the inhibitor takes place of the substrate and thus minimizes the catalytic property of enzyme. The non-competitive inhibitors do not bind to the active site of the enzyme. The non-competitive inhibitors bind to any other site of the enzyme and change the structure of the enzyme. The structure of active site is also changed because the structure of enzyme is changed by the inhibitors and thus the specific three dimensional active site of the enzyme is no longer available for the substrate to bind and form enzyme-substrate complex.

Higher substrate concentration decreases the chance of binding of inhibitors to the enzyme and thus maintain the velocity Vmax of the reaction. (Murray 2009; Vasudevan et al 2005) In last the competitive inhibitors bind to active site of enzyme but non-competitive inhibitors can bind to any site of enzyme except active site. In case of competitive inhibitors the higher substrate concentration decreases the possibility of inhibitor binding to the enzyme and on the other hand the non-competitive inhibitors are not affected by the substrate concentration (Chatterjea et al 2007; Murray 2009).

References CHATTERJEA, M. N., & SHINDE, R. (2007). Textbook of medical biochemistry. New Delhi, Jaypee Brothers Medical Publications (P) Ltd. Top of Form MURRAY, R. K. (2009). Harper's illustrated biochemistry. New York, McGraw-Hill Medical. Top of Form VASUDEVAN, D. M., & SREEKUMARI, S. (2005).Textbook of biochemistry for medical students. New Delhi, Jaypee Brothers Medical Publishers. Bottom of Form Top of Form Bottom of Form Bottom of Form