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Updated: Jun 8, 2026
09:47
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
How immune peptidases change specificity: cathepsin G gained tryptic function but lost efficiency during primate
Wilfred W Raymond1, Neil N Trivedi, Anastasia Makarova
1Cardiovascular Research Institute, University of California at San Francisco, San Francisco, CA 94143, USA.
Journal of Immunology (Baltimore, Md. : 1950)
|October 5, 2010
Summary
Human cathepsin G
Area of Science:
- Biochemistry
- Immunology
- Evolutionary Biology
Background:
- Cathepsin G (CG) is a neutrophil and mast cell serine peptidase.
- CG plays roles in antimicrobial defense and host tissue injury.
- Human CG exhibits dual tryptic and chymotryptic activity, unlike mouse CG.
Purpose of the Study:
- To investigate the evolutionary basis of human CG's dual specificity.
- To compare human and mouse CG activity and identify key structural differences.
- To explore the functional consequences of altered CG specificity.
Main Methods:
- Comparative analysis of human, mouse, and engineered CG variants.
- Enzyme activity assays measuring cleavage at various peptide sites.
- Phylogenetic analysis of CG evolution in primates.
Main Results:
- Mouse CG shows narrower specificity, favoring tyrosine cleavage and resisting inhibitors.
- Human CG exhibits broader specificity, including significant tryptic activity.
- Engineered mouse CG with Glu(226) gained tryptic activity and prourokinase activation.
- Phylogenetic analysis points to a specific mutation in primates driving tryptic activity.
Conclusions:
- Ancestral mammalian CG was likely primarily chymotryptic.
- A specific missense mutation in primates (Ala226Glu) uniquely introduced tryptic activity.
- This broadened specificity allowed CG to acquire new functions, diverging from typical immune peptidase specialization.
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