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The Proteasome

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 Proteasome

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...

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Related Experiment Video

Updated: Jul 14, 2026

The Determination of Protease Specificity in Mouse Tissue Extracts by MALDI-TOF Mass Spectrometry: Manipulating PH to Cause Specificity Changes

The Determination of Protease Specificity in Mouse Tissue Extracts by MALDI-TOF Mass Spectrometry: Manipulating PH to Cause Specificity Changes

Published on: May 25, 2018

Proteases in doping control analysis.

M Thevis¹, J Maurer, M Kohler

¹Center for Preventive Doping Research - Institute of Biochemistry, German Sport University Cologne, Cologne, Germany. thevis@dshs-koeln.de

International Journal of Sports Medicine

|May 26, 2007

Summary

Doping control laboratories face urine manipulation challenges. This study developed a method to detect proteases, enzymes used to degrade proteins and mask drug detection in athlete urine samples.

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Last Updated: Jul 14, 2026

The Determination of Protease Specificity in Mouse Tissue Extracts by MALDI-TOF Mass Spectrometry: Manipulating PH to Cause Specificity Changes

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Detection of Protein Ubiquitination Sites by Peptide Enrichment and Mass Spectrometry

Detection of Protein Ubiquitination Sites by Peptide Enrichment and Mass Spectrometry

Published on: March 23, 2020

Area of Science:

Forensic Science
Biochemistry
Analytical Chemistry

Background:

Urine manipulation is a significant issue in sports drug testing, potentially hindering the detection of performance-enhancing drugs like erythropoietin (EPO).
Proteases are suspected agents used in urine manipulation to degrade target drug molecules or biomarkers.

Purpose of the Study:

To develop and validate a protocol for detecting elevated protease activity in doping control specimens.
To visualize protein degradation indicative of protease activity.
To identify specific proteases present in manipulated urine samples.

Main Methods:

Utilized protease detection kits with fluorescein isothiocyanate-labeled casein.
Employed 1-dimensional gel electrophoresis to visualize protein degradation.
Applied bottom-up sequencing via in-gel digestion and liquid chromatography-Orbitrap tandem mass spectrometry for protease identification.

Main Results:

A protocol was established to determine elevated protease activities in urine.
Protease concentrations above 15 microg/mL led to observable protein degradation.
Specific proteases (chymotrypsin, trypsin, papain) were identified, and their detection persisted after prolonged storage.

Conclusions:

The developed protocol effectively detects protease activity and identifies specific enzymes in manipulated urine samples.
This method aids doping control laboratories in identifying urine tampering.
The findings contribute to safeguarding the integrity of sports drug testing.