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Specific inactivation of cysteine protease-type cathepsin by singlet oxygen generated from naphthalene endoperoxides

Yuki Nagaoka1, Kaoru Otsu, Futoshi Okada

  • 1Department of Biomolecular Function, Graduate School of Medical Science, Yamagata University, Japan.

Biochemical and Biophysical Research Communications
|April 23, 2005
PubMed

Insights

Singlet oxygen irreversibly inactivates cysteine proteases, like cathepsin B, by modifying essential catalytic amino acids. This finding is crucial for understanding photoaging and photodynamic therapy effects on cells.

Area of Science:

  • Biochemistry
  • Cell Biology
  • Dermatology

Background:

  • Singlet oxygen contributes to skin photoaging and tumor cell death in photodynamic therapy.
  • Understanding protein modification by singlet oxygen is key to its biological effects.

Purpose of the Study:

  • To investigate the impact of singlet oxygen on lysosomal proteases, specifically cathepsins.
  • To elucidate the functional consequences of singlet oxygen-induced protein modification.

Main Methods:

  • Treatment of soluble fractions from human fetal skin fibroblast cells with naphthalene endoperoxide.
  • Assay of cathepsin activities (cysteine and aspartate proteases) after treatment.
  • Examination of activity recovery using dithiothreitol reduction.
  • Analysis of purified cathepsin B activity.

Main Results:

  • Singlet oxygen inhibited cysteine proteases (cathepsins B and L/S) but not aspartate proteases (cathepsin D/E).
  • Dithiothreitol treatment minimally restored enzyme activity, suggesting irreversible modification.
  • Purified cathepsin B showed similar inactivation profiles.

Conclusions:

  • Singlet oxygen causes irreversible inactivation of cysteine protease-type cathepsins.
  • This inactivation is likely due to oxidative modification of a critical catalytic amino acid residue.
  • The findings have implications for photoaging and photodynamic cancer therapy.

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