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Control of exocellular proteases in dermatophytes and especially Trichophyton rubrum
Abstract:
The production of proteases was investigated during growth of dermatophytic fungi with special emphasis on Trichophyton rubrum. Exogenous glucose suppressed elastase production in all dermatophytes examined. The production of protease active guinea pig hair in keratin-salts broth by Microsporum gypseum. Trichophyton mentagrophytes and T. rubrum was also suppressed by glucose. Various carbohydrates added to keratin-salts broth curtailed protease production by T. rubrum as did individual amino acids but ammonium phosphate did not. Enzyme activities against guinea pig hair were compared in twenty-one diverse clinical isolates of T. rubrum cultured in keratin-salts broth. Activity also occurred towards casein, bovine serum albumin, keratin, collagen and elastin after keratin-growth. Studies concerning the properties of enzyme activities in culture filtrates of T. rubrum after keratin-growth suggested that multiple proteases occurred here. Hydrolysis of guinea pig hair and elastin were optimal at pH7 while keratinase was most active at alkaline pH. Divalent cations stimulated protease(s). Ferric ion and mercuric ion stimulated keratinase but were inhibitory to guinea pig hair hydrolysis and elastase. Chelating agents inhibited elastase and the hydrolysis of guinea pig hair more severely than keratinase and all of those effects were reversed by excess calcium. A serine-protease inhibitor, phenylmethylsulfonylfluoride (PMSF), curtailed keratinase but was less inhibitory to elastase and guinea pig hair hydrolysis. Soybean trypsin inhibitor arrested each protease.
Insights
Dermatophytic fungi, especially Trichophyton rubrum, produce proteases that degrade proteins like keratin. Glucose and other nutrients suppress protease production, while specific ions and inhibitors reveal distinct enzyme properties.
Area of Science:
- Mycology
- Biochemistry
Background:
- Dermatophytic fungi cause superficial infections by degrading keratin.
- Understanding their secreted proteases is crucial for developing antifungal strategies.
Purpose of the Study:
- To investigate protease production in dermatophytic fungi, focusing on Trichophyton rubrum.
- To characterize the enzymes involved in keratin degradation.
Main Methods:
- Culturing dermatophytes in keratin-salts broth.
- Assessing protease activity against various substrates (guinea pig hair, casein, collagen, elastin).
- Evaluating the effects of glucose, carbohydrates, amino acids, ions, and inhibitors on enzyme production and activity.
Main Results:
- Exogenous glucose significantly suppressed elastase production in all tested dermatophytes.
- Protease production by T. rubrum was inhibited by glucose, carbohydrates, and amino acids, but not ammonium phosphate.
- Multiple proteases were identified, with distinct pH optima and sensitivities to metal ions and inhibitors.
- Keratinase activity was optimal at alkaline pH, while guinea pig hair and elastin hydrolysis were optimal at pH 7.
- Serine protease inhibitor (PMSF) affected keratinase and other proteases differently.
Conclusions:
- Trichophyton rubrum produces multiple proteases with varying substrate specificities and properties.
- Nutrient availability, particularly glucose, plays a significant role in regulating protease production.
- Divalent cations and specific inhibitors provide insights into the catalytic mechanisms of these fungal enzymes.
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