Reviewing Mechanistic Peptidomics in Body Fluids Focusing on Proteases.

The comprehension of how protease networks sculpt proteomes might help to disclose the functional annotation of the peptidome in health and disease. Envisioning to add new insights on the protease networks involved in the regulation of body fluid peptidomes, the authors apply Proteasix software to predict the proteases involved in the generation of the naturally occurring peptides present in six of the most studied human body fluids. Peptidome data is collected from the databases and from experimental studies. The analysis highlights 132 putative proteases from four families with the predominance of serine proteases and metalloproteases. From these, 49 proteases seem to be common to all fluids and are mostly associated to extracellular matrix organization as well as protein/peptide hormone processing. Data analysis also emphasizes: i) the similarity between plasma and CSF protease profiles; ii) that saliva and tears share proteases involved in the generation of peptides with antimicrobial activity; iii) that urine is the body fluid with the highest number of unique putative proteases, precluding an easy tracing of proteolytic events in this case. Taken together, the analysis emphasizes the intricate modus operandi of proteases, challenged by the interconnected pathways and amplification cascades in which they are involved.