Primary substrate specificities of secreted aspartic proteases of Candida albicans.

Abstract

Candidiasis is an opportunistic infection of a pathogenic yeast of the genus Candida. These otherwise benign commensals become opportunistically invasive in response to impaired host defense mechanisms. Prominent among putative virulence factors are the secreted aspartic proteases, or Saps (Goldman et al., 1995; Ruchel et al., 1992; Cutler, 1991) which are implicated by biochemical, genetic, and immunochemical evidence. Multiple genes encoding Saps have been identified in the genome of clinical isolates of Candida species (Monod et al., 1994). In the most virulent species, C. albicans, seven genes have been cloned (SAP1—SAP7; Monod et al., 1994). The induction of SAP gene expression is strictly regulated in accord with changes in cell phenotype and morphology (Hube et al., 1994), implying that Candida albicans may require stage-specific proteases for its life cycle (Odds, 1994). Of these enzymes, SAP6 was found to be expressed exclusively in the virulent form of these cells, implying a direct invasive function (Hube et al., 1994; White and Agabian, 1995).