Cryptides: buried secrets in proteins

The proteome originally described the entire set of proteins expressed by a genome, tissue or organism. Subsequently this term was limited to all the expressed proteins at a given time under defined conditions. Hence, specializations such as functional proteome, cancer proteome, liver proteome and so forth have arisen. One particular proteome that has been recently described is the cryptome, a unique subset of already known proteins that has the ability of generating bioactive peptides and proteins when submitted to proteolytic cleavage, rather than the classical processing pathways. This is an idea in agreement with the concept that evolution is not related to the amount of genes or putative proteins that could be secreted by an organism, but to the way these proteins are processed. These ‘new’ molecules may have related or increased properties when compared to the ‘original’ molecule or possess completely unrelated biological effects, thus increasing the array of biological roles that can be associated to one given protein (or gene). In this work, we review this recent concept and put it into the toxinology field as well, an area in which the diversity of functional molecules (and roles) is essential for the survival of a given organism.