Proteolytic activity of Candida albicans: action on human salivary proteins

The susceptibility of human salivary proteins to degradation by Candida albicans was studied. The organism was cultivated in either whole-salivary supernatant or parotid fluid, both of which were supplemented with glucose (0.1%). The culture pH's were at, or above, neutrality. After growth, the culture supernatant solutions were examined by polyacrylamide gel electrophoresis for alterations in their profiles of salivary proteins. No evidence of proteolysis of whole-saliva or parotid fluid proteins was found. Salivary proteins, however, are susceptible to degradation by preparations of C. albicans protease. Candida protease was incubated with parotid fluid adjusted to several pH values. After incubation the reaction mixtures were subjected to polyacrylamide gel electrophoresis. Extensive degradation of parotid proteins was found at pH 4, very slight proteolysis at pH 5, and no degradation at pH 6 or 7. No selectivity in proteolysis of the several parotid proteins was noted. These results indicate that C. albicans protease is strictly dependent upon low (ca. 4) pH for activity on salivary proteins. Furthermore, it is suggested that due to the pH requirements of the enzyme, it is unlikely to be of major significance to the pathogenesis of Candida-induced oral inflammatory lesions.