Is Enzyme Inhibited: 7 Interesting Facts (Read This First)


In this article we are focusing on the topic “Is Enzyme Inhibited: 7 Interesting Facts (Read This First)”, giving the supporting statements and facts supporting the topic.

Enzyme inhibitor is defined as any substance that causes halts the enzyme substrate binding reaction. It causes a prevention in the reaction that suppose to occur as a result of the binding of an enzyme with its substrate. Enzymes act as a catalyst in a chemical reaction an inhibitor prevents the activity of an enzyme by binding to it.

There are varieties of enzyme inhibitors that are found naturally as well as produced in labs. Inhibitors that are naturally produced from the plant extracts are, Bidens pilosa, Cassia alata, Capsicum frutescens, Ficus carica, etc. chemically produced inhibitors are, Lepirudin, Bivalirudin, Cyclosporine, Ramiprill, Masoprocol, etc.

What is an Enzyme?

Enzymes are known as natural catalysts and are made up of amino acids, containing one or multiple polypeptide chains, hence they are called proteins by structure but not all proteins act as enzyme. The biological function of enzymes is to speed up any chemical reaction happening inside the living organisms.

Enzymes functions by binding to specific molecules and makes them activated by inducing certain morphological changes in the molecule. They play significant role in the biological processes like, respiration, digestion, wound healing, cell division, reproduction, etc. Enzymes catalyze any chemical reaction by addition, removal or transferring chemical groups, atoms or electrons.

is enzyme inhibited
Enzyme-Substrate complex Image from Wikipedia

Types of enzymes

Enzyme TypeFunction
OxidoreductasesTheir role is to catalyze the oxidation- reduction reactions by transferring of electrons mainly hydrogen atoms or hydride ions to the acceptor oxygen atom.
TransferasesAs the name suggests, they catalyze transfer reactions where transfer of group from a donor to the acceptor, for example Hexokinase enzyme.
HydrolasesThey catalyze hydrolysis reactions, which involves the transfer of a chemical group to the water. It is a type of transferase reaction where a functional group is being transferred from the donor to the water as an acceptor.
LyasesThey catalyze reactions by removal and addition of functional group to break or form a double bond.
IsomerasesThey catalyze the transfer of a chemical group within a molecule as a result of which isomeric forms are produced which changes the geometry and structure of the compound.
LigasesLigases are the glue enzyme they catalyze the formation of chemical bonds to join the two substrates together, the reactions are called condensation reactions. They require energy in the form of ATP to catalyze the reactions.
TranslocaseThey are present within the cell membranes where they assist and catalyze the movement of ion and other molecules in and out of the membrane.
Table showing Types of Enzymes

Types of enzyme Inhibition

  • Reversible Inhibition: here the enzyme- inhibitor binding is not strong but rather weak on-covalent interactions like; hydrogen bonds, ionic bonds and hydrophobic bonds. They are further categorized in four types.
  • Irreversible inhibition: the enzymes undergoing irreversible inhibition binds strongly with the inhibitor via covalent bonds. The irreversible inhibitors are of three types.
    • Group-specific reagents
    • Reactive substrate analogs (Affinity labels)
    • Suicide inhibitors

Difference between reversible and irreversible enzyme inhibition

S.no.ReversibleIrreversible
 1.Enzymes undergoing reversible inhibition follow Michaelis-Menten equation.Enzymes undergoing irreversible inhibition do not follow Michaelis-Menten equation.
2.  Inhibitor binds loosely with the target enzyme and dissociates rapidly.Inhibitor binds tightly to the active site of the enzyme and dissociates slowly.
 3.The type of bonding here is, weak non covalent, hydrogen bonds, and ionic bonds.Here, the binding could be covalent or non-covalent.
 4.They are classified into three types; competitive, non-competitive and mixed inhibition.They are classified into three types; group specific reagents, suicide inhibitors, and substrate analogs.
Difference between reversible and irreversible enzyme inhibition

What does inhibition mean in Enzymes?

Enzyme inhibition refers to the process where all the enzyme related processes and the enzyme activity is reduced. The enzyme inhibitors alter the enzyme activity by destroying their normal structure. Enzyme inhibitors are certain chemical and biological substances that modulate the enzyme activity.

The enzyme inhibitors contain the similar structure and chemical properties as of the substrates that suppose to bind in the active site of the enzyme but instead of substrates inhibitor binds to it, such an inhibition is called competitive inhibition.

Why enzymes are inhibited?

Enzymes are inhibited during many biological processes and hence inhibitors play significant roles in a biological system. Enzyme inhibitors prevents the formation of enzyme substrate complex formation.

Enzymes are inhibited when they are overexpressed or when they show hyperactivity. Inhibitors can be beneficial in a chemical reaction in many ways such as, to prevent side reactions, to control the temperature of the reaction, etc.

When enzymes are inhibited?

Enzymes can be highly regulated using activators and inhibitors. An activator increases an enzyme activity whereas an inhibitor decreases an enzyme activity and completely alters its normal function. An inhibitor can either bind to the active site or an allosteric site on an enzyme and halt a chemical reaction occurring inside a cell.

In the presence of inhibitor molecules enzyme inhibition occurs, they can act reversibly or irreversibly on the enzyme and stops the formation of enzyme-substrate complex.  

Which enzymes are inhibited?

Almost all the enzymes are inhibited by the presence of specific inhibitors. Certain synthetic inhibitors are malathion, herbicides, acetylcholinesterase. Inhibitors can bind either to the active site or to the allosteric site on the enzyme to prevent the enzyme-substrate formation and hence the product formation.

How does an enzyme get inhibited?

An enzyme is inhibited by the presence of certain molecules that binds to the enzymes in different ways temporarily or permanently and inhibit the enzyme to function normally. Inhibitor molecule binds to the enzyme either on the binding site or to any other site on enzyme in such a way that the reaction is stopped.

Enzyme inhibitor can bind reversibly or irreversibly using different bonding mechanisms and compete with the substrate for the same active site and sometime it binds with the enzyme even when substrate is bind to it. The inhibition is named based on the mechanism inhibitor uses.

What happens when enzyme is inhibited?

When an enzyme is inhibited reversibly or irreversibly it ultimately halts the process. In a normal process, enzyme helps in speeding up any chemical reaction by binding to the substrate to produce a product and then leave the substrate without being consumed in the reaction.

During inhibition the active site of the enzyme is occupied by the inhibitor which is similar to the substrate and is enzyme specific. As a result, enzyme is no longer able to function normally as it does in the absence of inhibitor. Certain enzyme inhibitors are used as an aid for the prevention of various genetic and physical abnormalities.

What is the importance of enzyme inhibitors?

Enzyme inhibition is an important biological control mechanism occurring inside the living system. Enzyme inhibitors are enzyme specific and are significant in controlling the activity of that particular enzyme. Enzyme inhibitors can reduce or completely stop the enzyme function.

Enzyme inhibitors helps in stopping the chemical reactions and hence the biological processes when the product formation is too high such an inhibition which is caused by the product itself is known as Feedback inhibition or negative feedback. Enzyme inhibitors play an important role in metabolic regulation for example, glycolytic pathway.

Conclusion

To conclude the article, we can say that enzymes are inhibited by the presence of certain chemicals known as inhibiters which binds to the enzyme specifically and alters the activity of the enzyme and ultimately stops the reaction.

Sneha Sah

Hey! I am Sneha Sah, I have completed post graduation in Biotechnology. Science has always been fascinating to me and writing is my passion. As an academic writer my aim is to make Science easy and simple to learn and read. Reach me at- Snehashah14111996@gmail.com

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