**2. Physiological role of metalloproteinases**

MMP-1 (collagenase 1) hydrolyzes collagen types I, II, III, VII, VIII, X and XI, as well as gelatin, fibronectin, vitronectin, laminin, tenascin, aggrecan, links protein, myelin basic protein and versican. MMP-2 (gellatinase) degrades collagen types I, II, III, IV, V, VII, X and XI, gelatin, elastin, fibronectin, vitronectin, laminin, entactin, tenascin, SPARC and aggrecan, links protein, galectin-3, versican, decanin and myelin basic protein. One of the most important differences between theses two metalloproteinases is the possibility of the hydrolysis of elastin and collagen type IV by MMP-2, but not by MMP-1. Researches have also focused their interest on MMP-9 which can degrade collagen types IV, V, VII, X and XIV, fibronectin, laminin, nidogen, proteoglycan link protein and versican.

For a long time metalloproteinases have been vied solely as enzymes of matrix proteins breakdown. Results of researches performed in recent years indicate that there is a group of

© 2012 Siemianowicz, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

non-matrix proteins which can be substrates for various MMPs. Metalloproteinases are involved in the activation of latent forms of effective proteins. For example, MMP-2, MMP-3 and MMP-9 can activate interleukin 1 (IL-1). They can also act on active cytokines, IL-1 undergoes subsequent degradation catalyzed by MMP-3. Metalloproteinases can alter cell surface proteins such as receptors and act on microbial peptides.

Metalloproteinases are not indiscriminately released by cells. They are secreted to or anchored to cell membrane. MT-MMPs have a specific transmembrane domain placing them in a certain position. Other metalloproteinases can be bound by specific cell-MMP interactions. This phenomenon allows an exact localization of their proteolytic activity [1,2].
