Considerable progress has been made in our understanding of the specificity and the mechanism of action of serine-, cysteine- and metalloproteinases and their natural and synthetic inhibitors by crystallographic structural studies.

On the basis of these structures, structure-based design of proteinase inhibitors for therapy of diseases related to uncontrolled proteinase activity is possible. Such studies can be extended to to all families of proteolytic enzymes including the very large protease complexes, the proteasome and related Hs1V, whose structures have been elucidated.