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Related Concept Videos

Enzyme Inhibition01:30

Enzyme Inhibition

Inhibitors are molecules that reduce enzyme activity by binding to the enzyme. In a normally functioning cell, enzymes are regulated by a variety of inhibitors. Drugs and other toxins can also inhibit enzymes. Some inhibitors bind to the enzyme’s active site, while others inhibit enzymatic activity by binding to other sites on the protein structure.
Enzymes02:34

Enzymes

Inside living organisms, enzymes act as catalysts for many biochemical reactions involved in cellular metabolism. The role of enzymes is to reduce the activation energies of biochemical reactions by forming complexes with its substrates. The lowering of activation energies favor an increase in the rates of biochemical reactions.
Enzyme deficiencies can often translate into life-threatening diseases. For example, a genetic abnormality resulting in the deficiency of the enzyme G6PD...
Indirect-Acting Cholinergic Agonists: Mechanism of Action01:18

Indirect-Acting Cholinergic Agonists: Mechanism of Action

Indirect-acting cholinergic agonists work by interacting with an enzyme called acetylcholinesterase (AChE) in the synaptic cleft. They can be reversible or irreversible inhibitors and have different effects on the enzyme.
Reversible inhibitors like edrophonium bind to a specific part of the enzyme called the anionic catalytic site. They form noncovalent bonds, which means they are not strongly attached to the enzyme. This creates a temporary and less stable enzyme–inhibitor complex, leading to...
Feedback Inhibition00:46

Feedback Inhibition

Biochemical reactions are occurring constantly in cells, converting starting substances to different products, usually with the help of enzymes that speed the reactions. Without enzymes, it would take far too long for most reactions to occur to be useful to the cell!
Induced-fit Model01:13

Induced-fit Model

Most chemical reactions in cells require enzymes—biological catalysts that speed up the reaction without being consumed or permanently changed. They reduce the activation energy needed to convert the reactants into products. Enzymes are proteins, that usually work by binding to a substrate—a reactant molecule that they act upon.
Enzymes exhibit substrate specificity, meaning that they can only bind to certain substrates. This is mainly determined by the shape and chemical characteristics of...
Ligand Binding Sites02:40

Ligand Binding Sites

Proteins are dynamic macromolecules that carry out a wide variety of essential processes; however, the activities of most proteins depend on their interactions with other molecules or ions, known as ligands.
Protein-ligand interactions are quite specific; even though numerous potential ligands surround a cellular protein at any given time, only a particular ligand can bind to that protein. Moreover, a ligand binds only to a dedicated area on the surface of the protein, known as the...

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Related Experiment Video

Updated: Jun 14, 2026

A Semi-High-Throughput Adaptation of the NADH-Coupled ATPase Assay for Screening Small Molecule Inhibitors
10:28

A Semi-High-Throughput Adaptation of the NADH-Coupled ATPase Assay for Screening Small Molecule Inhibitors

Published on: August 17, 2019

Non-competitive inhibition by active site binders.

Yuval Blat1

  • 1Department of Mechanistic Biochemistry, Bristol-Myers Squibb Company, Rt. 206 and Provinceline Rd., Princeton, NJ 08543, USA. yuval.blat@bms.com

Chemical Biology & Drug Design
|April 9, 2010
PubMed
Summary

Enzyme kinetics experiments can identify active site inhibitors, but some inhibitors binding to the active site may not compete with substrates. Advanced enzymology tools help distinguish these

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Development of Inhibitors of Protein-protein Interactions through REPLACE: Application to the Design and Development Non-ATP Competitive CDK Inhibitors
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Development of Inhibitors of Protein-protein Interactions through REPLACE: Application to the Design and Development Non-ATP Competitive CDK Inhibitors

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Published on: August 17, 2019

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Bio-layer Interferometry for Measuring Kinetics of Protein-protein Interactions and Allosteric Ligand Effects

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Development of Inhibitors of Protein-protein Interactions through REPLACE: Application to the Design and Development Non-ATP Competitive CDK Inhibitors
10:33

Development of Inhibitors of Protein-protein Interactions through REPLACE: Application to the Design and Development Non-ATP Competitive CDK Inhibitors

Published on: October 26, 2015

Area of Science:

  • Biochemistry
  • Enzyme kinetics
  • Drug discovery

Background:

  • Classical enzymology relies on substrate-inhibitor competition assays to determine inhibitor binding sites.
  • Inhibitors binding to an enzyme's active site typically compete with the substrate.
  • Exceptions exist where active site inhibitors do not compete with substrates.

Purpose of the Study:

  • To explore exceptions to the rule that active site inhibitors compete with substrates.
  • To understand the mechanisms behind non-competitive inhibition patterns observed with active site binders.
  • To present methods for distinguishing true exosite inhibitors from atypical active site binders.

Main Methods:

  • Enzyme kinetics assays
  • Analysis of inhibition patterns (competitive vs. non-competitive)
  • Utilizing alternative substrates
  • Assessing reaction reversibility
  • Monitoring inhibition time-dependence

Main Results:

  • Active site-binding inhibitors can exhibit non-competitive inhibition.
  • This phenomenon is observed in enzymes with exosites, multiple substrates/products, or complex binding mechanisms.
  • Distinguishing these cases from true exosite inhibition requires careful mechanistic studies.

Conclusions:

  • Substrate-inhibitor competition is not always indicative of inhibitor binding site.
  • Enzymology offers tools to resolve complex inhibition patterns.
  • Accurate inhibitor characterization is crucial for drug development.