Cloning and sequencing of two Candida parapsilosis genes encoding acid proteases

Candida parapsilosis secretes an inducible acid protease (ACP) when cultivated in the presence of bovine serum albumin as the sole nitrogen source. In order to clone the ACP gene (ACP) of C. parapsilosis, a genomic library was screened with C. tropicalis ACP as the probe. Two different ORFs, ACPR and ACPL, were found to hybridize with the C. tropicalis ACP. ACPR contained a DNA sequence in agreement with the N-terminal amino acid sequence of C. parapsilosis ACP isolated from culture supernatants. ACPR was shown to be expressed and functional in a C. tropicalis acid protease mutant (acp) and with SDS-PAGE the protein product showed the same mobility as the ACP secreted by C. parapsilosis. These results imply that ACPR encodes the C. parapsilosis ACP. The deduced amino acid sequence of ACPR is similar to the amino acid sequence of proteases of the pepsin family. As in the case of the C. tropicalis and C. albicans ACP, the 5' extremity of ACPR revealed a propeptide containing two Lys-Arg amino acid pairs that have been identified as peptidase processing sites in several yeast-secreted peptides and protein precursors. As judged from the deduced amino acid sequences, the ACPL product would be similar to that of ACPR; however, a protein corresponding to ACPL was not found in supernatants from C. parapsilosis liquid cultures. In addition, ACPL did not complement the C. tropicalis acp mutant. We conclude that ACPL is a pseudogene or serves an as yet unidentified function.