Characterization of Candida albicans epidermolytic proteases and their role in yeast-cell adherence to keratinocytes.

Epidermolytic proteases were partially purified from six strains of Candida albicans, four of which were isolated from patients with cutaneous diseases. Two of the strains exhibited a unique time-course of enzyme production compared to that previously reported, with detectable epidermolytic protease levels being significantly delayed. All epidermolytic proteases had pH and temperature optima of 4-4.5 and 35-37 degrees C, respectively. These conditions are consistent with the microenvironment of human skin, a habitat where an epidermolytic protease would appear to be an important advantage to the yeast. Candida epidermolytic proteases were more active against a substrate of normal human epidermis than that obtained from psoriatic patients. When human epidermis replaced bovine serum albumin as the protein source within the culture medium, the epidermolytic activity of the resultant enzyme was reduced by 9 and 25% for normal and psoriatic epidermis substrates, respectively. The proteases were found to contain major protein bands at 42 and 66 kDa. The ability of these same Candida strains to adhere to human epidermal cells was studied and found to be optimal at 35-37 degrees C within neutral pH values. Pepstatin, bovine brain gangliosides, and convalescent human serum all interfered with the adherence of the yeast to epidermal cells. A higher yeast-epidermal-cell adherence for Candida was demonstrated on normal rather than psoriatic epidermal cells, and after treating the cells with partially purified Candida protease.