Control of exocellular proteases in dermatophytes and especiallyTrichophyton rubrum

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Abstract
The production of proteases was investigated during growth of dermatophytic fungi with special emphasis on T. rubrum. Exogenous glucose suppressed elastase production in all dermatophytes examined. The production of protease active against guinea pig hair in keratin-salts broth by Microsporum gypseum, T. mentagrophytes and T. rubrum was suppressed by glucose. Various carbohydrates added to keratin-salts broth curtailed protease production by T. rubrum as did individual amino acids but (NH4)3PO4 did not. Enzyme activities against guinea pig hair were compared in 21 diverse clinical isolates of T. rubrum cultured in keratin-salts broth. Activity 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 pH 7 while keratinase was most active at alkaline pH. Divalent cations stimulated protease(s). Fe3+ and Hg3+ 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 Ca. 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. [These proteases may play a prominent role in invasion of host tissues and may contribute to hypersensitivity reactions].

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