In the last few years proteolysis has attracted special attention, which is connected with development of proteomics - one of the most important trends of «postgenomic era» biochemistry, providing for inventory of all human proteins, both when normal and pathologic. That is why the knowledge of processes determining the protein life is necessary for a modern specialist in the field of medical biochemistry. This publication is the third of the planned series of reviews, dedicated to different aspects of proteolysis. The previous two focused on its overall description, and also on classification and mechanisms of proteinases activities.