Difference Between Enzyme Inhibitor and Enzyme Inducer

The key difference between enzyme inhibitor and enzyme inducer is that enzyme inhibitor decreases the activity of an enzyme by binding with the active site of the enzyme. In contrast, enzyme inducer increases the metabolic activity of an enzyme either by binding to it or by increasing the gene expression.

Enzymes are the biomolecules that catalyze biochemical reactions occurring in living cells. They increase the rate of reactions by lowering their activation energies. Substrates bind with the active site of the enzyme and form the substrate-enzyme complex. Then the substrate transforms into the product, leaving the enzyme behind unchanged. Enzyme inhibitors decrease the activity or catalytic ability of an enzyme, binding with the active site of it. In contrast, enzyme inducer increases the activity of the enzyme by binding or by enhancing the expression of the gene that is coding the enzyme.

CONTENTS

1. Overview and Key Difference
2. What is Enzyme Inhibitor 
3. What is Enzyme Inducer
4. Similarities Between Enzyme Inhibitor and Enzyme Inducer
5. Side by Side Comparison – Enzyme Inhibitor vs Enzyme Inducer in Tabular Form
6. Summary

What is an Enzyme Inhibitor?

An enzyme inhibitor is a molecule that decreases the enzyme activity by binding to it. Most enzyme inhibitors bind to the active site of the enzyme and prevent the formation of the enzyme-substrate complex. Therefore, the inhibitor competes with the substrate for binding with the active site of the enzyme. If an enzyme fails to bind with the substrate, its catalytic activity reduces. Hence, at the end of the reaction, the amount of product is low. In fact, the amount of product produced is inversely proportional to the concentration of inhibitor molecules.

The binding of an inhibitor to an enzyme can be reversible or irreversible. Reversible inhibitors bind non-covalently with the enzyme, forming hydrogen bonds, hydrophobic interactions and ionic bonds while irreversible inhibitors bind covalently. Irreversible inhibitors change the enzyme chemically by modifying its amino acid sequence. Once the amino acid sequence is altered, its activity reduces. Many types of drugs are enzyme inhibitors, especially antiretroviral drugs used to treat HIV.

What is an Enzyme Inducer?

Enzyme inducer is a molecule that increases the catalytic activity of an enzyme. It can induce the enzyme by binding with its active site and decreasing the enzyme degradation rate.  It can also increase the expression of the gene that encodes the enzyme in order to increase the total amount of enzyme involved in the reaction. Thus, enzyme inducer increases the synthesis of the enzyme by increasing the gene expression.

Many xenobiotics and environmental chemicals are enzyme inducers. Many drugs are also enzyme inducers. Rifampin is an anti TB drug which is a popular enzyme inducer. Moreover, carbamazepine, phenytoin and phenobarbital are several other enzyme inducers.

What are the Similarities Between Enzyme Inhibitor and Enzyme Inducer?

• Enzyme inducer and enzyme inhibitor are able to change the rate of enzyme activity.
• They are able to bind with the active site of an enzyme.
• Many drugs are enzyme inhibitors and enzyme inducers.
• Both types are important in the studies of drug metabolism.

What is the Difference Between Enzyme Inhibitor and Enzyme Inducer?

Enzyme inhibitor is a molecule that decreases the activity of an enzyme by binding with the active site of the enzyme while enzyme inducer is a molecule that increases the metabolic activity of an enzyme either by binding to it or by increasing the gene expression. So, this is the key difference between enzyme inhibitor and enzyme inducer.

Moreover, enzyme inhibitor reduces the amount of products while enzyme inducer increases the amount of products. Thus, this is another difference between enzyme inhibitor and enzyme inducer.

Summary – Enzyme Inhibitor vs Enzyme Inducer

Enzyme inhibitors are the molecules that bind with enzymes and reduce the enzyme activity. In contrast, enzyme inducers are molecules that increase the activity of an enzyme. Inducers decrease the degradation rate of the enzyme. Some inducers increase the expression of the gene which is responsible for the synthesis.  Therefore, the action of enzyme inhibitor reduces the amount of the product while the action of enzyme inducer increases the amount of product at the end. So, this is the summary of the difference between enzyme inhibitor and enzyme inducer.

Reference:

1. “Enzyme Inhibitor.” Wikipedia, Wikimedia Foundation, 10 Dec. 2019, Available here.
2. “Enzyme Inducer.” Enzyme Inducer – an Overview | ScienceDirect Topics, Available here.

Image Courtesy:

1. “DHFR methotrexate inhibitor” By Thomas Shafee – Own work (CC BY 4.0) via Commons Wikimedia
2. “Rifampicin structure” By Vaccinationist – Rifampicin on PubChem (Public Domain) via Commons Wikimedia