Secreted aspartic proteases of Candida albicans, Candida tropicalis, Candida parapsilosis and Candida lusitaniae - Inhibition with peptidomimetic inhibitors

The frequency of Candida infections has increased in recent years and it ha s been accompanied by a significant rise in morbidity and mortality. The se cretion of aspartic proteases by Candida spp. was demonstrated to be one of the virulence determinants. Candida albicans is classified as the major hu man pathogen in the genus Candida. However, other species of this genus hav e been found to cause an increasing number of candidiases. We isolated secr eted aspartic proteases (Saps) of C. albicans (Sap2p), C. tropicalis (Sapt1 p), C. parapsilosis (Sapp1p), and C. lusitaniae (Saplp) from culture media. All the isolated proteases were N-terminally sequenced. Their specific pro teolytic activities and sensitivity to series of peptidomimetic inhibitors modified in the type of scissile bond replacement as well as in the N- and C-termini were analyzed. The most divergent substrate specificity was obser ved for the Sap of C. tropicalis. The specificity of Sap of C. lusitaniae i s most closely related to that of Sap of C. parapsilosis. We designed and p repared an inhibitor containing phenylstatine isoster that was equipotent t owards all four proteases within the range of 10(-10)-10(-9) m. The HIV-1 p rotease inhibitors ritonavir, saquinavir, indinavir, and nelfinavir were al so tested for the inhibition of four Saps. Only ritonavir and saquinavir in hibited Sap2p, Sapt1p, Sapp1p, and Saplp in micromolar concentrations.