Introduction 

Enzymes are Catalysts that make reactions faster, Enzyme inhibitors are substances that bind to enzymes and decrease their activity. Two board classes of enzyme inhibitors are classified as Reversible enzymes and Irreversible enzymes. Reversible inhibitors bind temporarily with enzymes and after resealing of inhibitors from Enzymes, the rate of enzyme-catalyze reaction gets into its actual speed. Irreversible inhibitors deform the shape of enzymes permanently and stop enzymes from forming ES complex permanently. 

Enzyme Inhibition and Types of Inhibition

Enzyme inhibitors are temporary or permanent molecules that bind to enzymes and reduce the rate of enzyme-catalyzed reactions. There are different types of inhibitors such as competitive, noncompetitive and uncompetitive inhibitors. Competitive enzymes inhibit enzymes with similar shapes attached to the active site of enzymes thus inhibiting formation of Enzyme-substrate complexes. This process is reversible thus this binding is temporary. Degree of inhibition depends on relative concentration of inhibitor and the substrates, for example, Malonate is a competitive enzyme Inhibitor of the Enzyme Succinate Dehydrogenase where Substrate is Succinate.  Noncompetitive enzymes bind to enzymes other than active sites. Binding of Noncompetitive enzymes results in deformation of enzymes thus also called allosteric enzymes. Due to its deformity enzymes cannot form ES complexes. Glucose-6-phosphate is a well-known Noncompetitive enzyme that inhibits Hexokinase in Brain.  Uncompetitive enzymes bind to ES complex rather than Free enzymes and results in enzymatic inactivity. Inhibition of Aryl Sulphates by Hydrazine is a good example of an Uncompetitive enzyme Inhibitor. 

Enzyme inhibition

Enzyme inhibition refers to a decrease in enzyme-related process, enzyme activity or production of enzymes. This inhibition plays an important role in the discovery of drugs. Enzymes are effective bio catalyzes that accelerate almost all metabolic reactions in the body. Every enzyme has single or Multiple Substrate Binding sites or SBS where substrates bind and activate enzymes and thus accelerate Rate of reactions. Enzyme inhibitors bind to those substrate binding sites and prevent substrate from binding in the active sites thus reducing rates of enzyme-catalytic reactions. Irreversible inhibitors are Covalent Modifications of enzymes that ensure that chemical reaction between enzyme and inhibitor is not reversible. Inhibitors of small molecular size proved to be useful as a promoting agent for cancer chemotherapy. Leupeptin is identified as an inhibitor against serine or thiol proteases such as plasmin, papain and cathepsin. Nonspecific Inhibitors similarly affect all enzymes by denaturing the chemical and physical properties of enzymes thus this results in irreversible inhibition of enzymes. Activity of enzymes is controlled by pH and Temperature. Usually, reaction rate increases with temperature but after an optimum temperature protein denatures and inhibits reaction.  With increasing and decreasing pH rates the nature of acid and amine group’s changes and results in a change of the shape of enzymes. 

Types of Enzyme Inhibition

Enzyme Inhibition has been divided into three types of enzyme inhibition processes depending on what type of inhibitor it uses. These inhibitors can either be competitive or non-competitive. Types of enzyme inhibition include Allosteric inhibition, Phosphorylation and Zymogens. Allosteric enzymes have been known to provide a sigmoidal curve rather than a hyperbolic curve. This phenomenon happens due to multiple subunits in a single enzyme. Allosteric enzymes have been known to have two states called “T” state and “R” state. Different inhibitors bind to the T state of an Allosteric enzyme and cause this enzyme to maintain its T state. Inhibition of these enzymes has been known as Allosteric Inhibition.

Phosphorylation has been known as a mechanism by which an enzyme can be inhibited. This process has been known to occur due to Kinase enzymes. Kinase enzymes differentiate phosphate groups from ATP and bind them to an enzyme and this can create a cascade reaction.

 Enzymes when inhibited in an inactive state are known as Zymogens. This mechanism has been helpful in allowing enzymes to be safely moved to another location.

Competitive Enzyme Inhibition

In Competitive Enzyme Inhibition, inhibitors have been seen to compete with substrates at active sites. These inhibitors have been known as competitive inhibitors. Competitive inhibitors in an enzyme inhibition can increase the “Michaelis-Menten Constant” (Km). Vmax in competitive inhibitions has been seen to be unchanged due to substrate concentration. However, in non-competitive enzymes, inhibitors have been seen to decrease Vmax. Results of some enzyme inhibitions have been seen to be similar in structure to substrate resulting in competitive inhibition of the whole reaction. This process thus is also known as end-product inhibition. Variation of a competitive enzyme inhibition has been seen to be occasional. These variations also include build-up of end product reversing forward reaction and this results in regenerating the whole substrate. Different drugs have been known to be used as competitive inhibitors of different enzymes. For example, it has been seen that Angiotensin-Converting Enzyme (ACE) is mostly targeted by Antihypertensive drugs.

Conclusion

This assignment concluded enzyme inhibition and types of inhibition which can be seen in different enzymes depending on different types of inhibitors. It also concluded the definition of enzyme inhibition and types of enzyme inhibition. This assignment further concluded a detailed overview of competitive enzyme inhibition.