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Secreted proteases from dermatophytes
1Service de Dermatologie et Vénéréologie, Laboratoire de Mycologie, BT422, Centre Hospitalier Universitaire Vaudois, 1011 Lausanne, Switzerland. Michel.Monod@chuv.ch
Abstract:
Dermatophytes are highly specialized pathogenic fungi that exclusively infect the stratum corneum, nails or hair, and it is evident that secreted proteolytic activity is important for their virulence. Endo- and exoproteases-secreted by dermatophytes are similar to those of species of the genus Aspergillus. However, in contrast to Aspergillus spp., dermatophyte-secreted endoproteases are multiple and are members of two large protein families, the subtilisins (serine proteases) and the fungalysins (metalloproteases). In addition, dermatophytes excrete sulphite as a reducing agent. In the presence of sulphite, disulphide bounds of the keratin substrate are directly cleaved to cysteine and S-sulphocysteine, and reduced proteins become accessible for further digestion by various endo- and exoproteases secreted by the fungi. Sulphitolysis is likely to be an essential step in the digestion of compact keratinized tissues which precedes the action of all proteases.
Insights
Dermatophyte fungi use unique proteases and sulphite to break down keratin. This sulphitolysis process is essential for digesting tough skin, nail, and hair tissues, aiding fungal infection.
Area of Science:
- Mycology
- Biochemistry
- Dermatology
Background:
- Dermatophytes are specialized fungi causing infections of keratinized tissues.
- Proteolytic enzymes are crucial for dermatophyte virulence.
- Dermatophyte proteases share similarities with Aspergillus spp. proteases.
Purpose of the Study:
- To investigate the unique proteolytic mechanisms of dermatophytes.
- To understand the role of sulphite in keratin degradation by dermatophytes.
Main Methods:
- Analysis of secreted endo- and exoproteases.
- Investigation of sulphite excretion and its effect on keratin structure.
Main Results:
- Dermatophytes secrete multiple endoproteases belonging to subtilisin and fungalysin families.
- Dermatophytes excrete sulphite, a reducing agent.
- Sulphite directly cleaves disulfide bonds in keratin, facilitating protease access.
Conclusions:
- Sulphitolysis, involving sulphite action on keratin disulfide bonds, is a key step preceding protease digestion.
- This mechanism is essential for dermatophytes to degrade compact keratinized tissues.
- The dual action of sulphite and proteases enhances dermatophyte virulence.
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