In the past, singly-selected protease-substrates (proteins cleaved by enzymes) were tested by in vitro cleavage assays and thus substrate discovery was haphazard. Nowadays, with the rapidly growing field of proteomics (study of entire protein sub- sets of a cell), a protease and its substrate repertoire (degradome) may be studied in a complex context to identify physiologically relevant substrates. The author Daniel Ambort describes step- by-step first the principles of degradomics and then its application in protease-substrate discovery. Two biological systems, a cell-based (culture medium- derived proteins) and a cell-free (human milk as polysubstrate), were used to find hitherto unkown substrates for the metalloendopeptidase meprin (zinc- dependent protein-cleaving enzyme). One- and two- dimensional gel electrophoresis together with mass spectrometry enabled the identification of novel meprin cleavage products. In summary, this book combines standard textbook knowledge with laboratory- intense hard work and it thus encompasses a complete description of the realization of degradomics projects.