Related Experiment Video

Updated: Jun 19, 2026

A Fluorescence-based Protocol for Preliminary Screening of Protein Synthesis Inhibitors from Natural Sources
10:24

A Fluorescence-based Protocol for Preliminary Screening of Protein Synthesis Inhibitors from Natural Sources

Published on: January 27, 2026

Inhibitory effect of flavonoids on 26S proteasome activity

Tsui-Ling Chang1

  • 1Department of Biological Sciences and Technology, National University of Tainan, No. 33, Sec. 2, Shu-Lin Street, Tainan, Taiwan. tsuiling@mail.nutn.edu.tw

Journal of Agricultural and Food Chemistry
|October 3, 2009
PubMed

Insights

Flavonoids can inhibit the 26S proteasome, a key target for cancer therapy. Certain flavones, like 5,6,3

Area of Science:

  • Biochemistry
  • Pharmacology

Background:

  • Proteasomal degradation inhibition is a promising strategy for cancer therapy.
  • Certain flavonoids are known to induce apoptosis by inhibiting 26S proteasome activity.

Purpose of the Study:

  • To investigate the inhibitory effects of various flavonoids on 26S proteasome activity.
  • To identify specific flavonoid structures with potent anticancer potential.

Main Methods:

  • Analysis of 12 flavones, 5 flavanones, and 9 isoflavones using a proteolysis assay.
  • Assay of chymotrypsin-like, caspase-like, and trypsin-like proteasome activities using specific substrates.
  • Lineweaver-Burk plot analysis to determine inhibition types.

Main Results:

  • Several flavonoids, including apigenin-6-hydroxy-7-O-beta-D-glucoside, quercetin, and 5,6,3',4'-tetrahydroxy-7-methoxyflavone, inhibited proteasome activities.
  • Flavones demonstrated stronger inhibition of chymotrypsin-like and caspase-like activities compared to flavanones and isoflavones.
  • 5,6,3',4'-Tetrahydroxy-7-methoxyflavone exhibited the highest inhibitory effect, targeting all three peptidase activities and showing 75% casein degradation inhibition.

Conclusions:

  • The 6-hydroxy and 7-methoxy positions on the flavone structure are crucial for potent 26S proteasome inhibition.
  • 5,6,3',4'-Tetrahydroxy-7-methoxyflavone is a potent inhibitor of 26S proteasome activity, suggesting its potential as an anticancer agent.

More Related Videos

Cellular Redox Profiling Using High-content Microscopy11:37

Cellular Redox Profiling Using High-content Microscopy

Published on: May 14, 2017

Related Concept Videos

The Proteasome02:18

The Proteasome

Eukaryotic cells can degrade proteins through several pathways. One of the most important amongst these is the ubiquitin-proteasome pathway. It helps the cell eliminate the misfolded, damaged, or unwarranted cytoplasmic proteins in a highly specific manner.
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. A series of enzymes carry out the ubiquitination of the target proteins - E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...
The Proteasome01:13

The Proteasome

Eukaryotic cells can degrade proteins through several pathways. One of the most important among these is the ubiquitin-proteasome pathway. It helps the cell eliminate the misfolded, damaged, or unwarranted cytoplasmic proteins in a highly specific manner.
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. This involves participation of a series of enzymes including— E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3 (ubiquitin...
The Proteasome02:18

The Proteasome

Eukaryotic cells can degrade proteins through several pathways. One of the most important amongst these is the ubiquitin-proteasome pathway. It helps the cell eliminate the misfolded, damaged, or unwarranted cytoplasmic proteins in a highly specific manner.
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. A series of enzymes carry out the ubiquitination of the target proteins - E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...
The Proteasome Structure01:17

The Proteasome Structure

The ubiquitin-proteasome pathway is a well-known mechanism utilized by eukaryotic cells to remove cytoplasmic proteins that are misfolded, damaged, or no longer needed. In this pathway, the protein that needs to be eliminated undergoes a process called ubiquitination, where a chain of ubiquitin molecules is attached to the 48th lysine residue of the target protein. This ubiquitin modification helps the proteasome distinguish between a target protein and a healthy protein.
The proteasome is an...
Inhibitors of Bacterial Protein Synthesis01:25

Inhibitors of Bacterial Protein Synthesis

Aminoglycosides constitute a highly potent class of bactericidal antibiotics that exert their antimicrobial effects by targeting the bacterial ribosome, specifically disrupting protein synthesis. These polycationic molecules consist of amino-modified sugars linked via glycosidic bonds to an aminocyclitol core such as 2-deoxystreptamine or streptamine. Their strong positive charges facilitate tight binding to the negatively charged phosphate backbone of ribosomal RNA (rRNA), primarily at the 16S...
Inhibition of Cdk Activity02:34

Inhibition of Cdk Activity

The orderly progression of the cell cycle depends on the activation of Cdk protein by binding to its cyclin partner. However, the cell cycle must be restricted when undergoing abnormal changes. Most cancers correlate to the deregulated cell cycle, and since Cdks are a central component of the cell cycle, Cdk inhibitors are extensively studied to develop anticancer agents. For instance, cyclin D associates with several Cdks, such as Cdk 4/6, to form an active complex. The cyclin D-Cdk4/6 complex...