Fungal yapsins and cell wall: a unique family of aspartic peptidases for a distinctive cellular function.

A novel class of aspartic peptidases known as fungal yapsins, whose first member ScYps1p was identified more than a decade ago in Saccharomyces cerevisiae, is characteristically modified by the addition of a glycophosphatidylinositol moiety and has a preference for cleaving substrates C-terminally to mono- and paired-basic residues. Over the years, several other members, first in S. cerevisiae and then in other fungi, have been identified. The implication of fungal yapsins in cell-wall assembly and/or remodelling had been suspected for many years. However, it is only very recently that studies performed on S. cerevisae and Candida albicans have confirmed their importance for cell-wall integrity. Here, we review 16 years of research, covering all fundamental aspects of these unique enzymes, in an effort to track their functional significance. We also propose a nomenclature for fungal yapsins based on their sequence identity with the founding members of this family, the S. cerevisiae yapsins.