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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...
Allosteric Regulation01:08

Allosteric Regulation

Allosteric regulation of enzymes occurs when the binding of an effector molecule to a site that is different from the active site causes a change in the enzymatic activity. This alternate site is called an allosteric site, and an enzyme can contain more than one of these sites. Allosteric regulation can either be positive or negative, resulting in an increase or decrease in enzyme activity. Most enzymes that display allosteric regulation are metabolic enzymes involved in the degradation or...
Allosteric Regulation01:08

Allosteric Regulation

Allosteric regulation of enzymes occurs when the binding of an effector molecule to a site that is different from the active site causes a change in the enzymatic activity. This alternate site is called an allosteric site, and an enzyme can contain more than one of these sites. Allosteric regulation can either be positive or negative, resulting in an increase or decrease in enzyme activity. Most enzymes that display allosteric regulation are metabolic enzymes involved in the degradation or...
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!

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Related Experiment Video

Updated: Jul 10, 2026

Bio-layer Interferometry for Measuring Kinetics of Protein-protein Interactions and Allosteric Ligand Effects
13:57

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

Published on: February 18, 2014

Stochastic inhibitor release and binding from single-enzyme molecules.

Hans H Gorris1, David M Rissin, David R Walt

  • 1Department of Chemistry, Tufts University, 62 Talbot Avenue, Medford, MA 02155, USA.

Proceedings of the National Academy of Sciences of the United States of America
|October 30, 2007
PubMed
Summary

Researchers studied single beta-galactosidase enzyme molecules using a microfluidic array. They observed inhibitor d-galactal binding and release, revealing enzyme conformational changes and stochastic kinetics.

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Method for Identifying Small Molecule Inhibitors of the Protein-protein Interaction Between HCN1 and TRIP8b

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

Published on: August 17, 2019

Area of Science:

  • Biochemistry
  • Enzyme kinetics
  • Single-molecule analysis

Background:

  • Beta-galactosidase is a key enzyme in lactose metabolism.
  • Understanding enzyme inhibition is crucial for drug development.
  • Slow-binding inhibitors like d-galactal present unique kinetic challenges.

Purpose of the Study:

  • To characterize the inhibition kinetics of single beta-galactosidase molecules with d-galactal.
  • To investigate the stochastic nature of inhibitor binding and release.
  • To correlate single-molecule observations with bulk reaction kinetics.

Main Methods:

  • Utilized a microfluidic array of 50,000 ultra-small reaction containers.
  • Employed fluorescence microscopy to monitor substrate turnover of individual enzyme molecules.
  • Conducted pre-steady-state and steady-state experiments.

Main Results:

  • Successfully distinguished between inhibited and active states of single beta-galactosidase molecules.
  • Demonstrated the first-order kinetics of stochastic inhibitor release.
  • Observed repeated inhibitor binding/release events linked to catalytic site conformational changes.

Conclusions:

  • Single-molecule analysis provides high-resolution insights into enzyme inhibition.
  • The study confirms consistency between single-molecule and bulk reaction kinetics.
  • Characterization of d-galactal inhibition provides a model for slow-binding enzyme inhibitors.