Matrix metalloproteinases (MMPs) are a family of zinc- and calcium-dependent proteolytic enzymes. In humans, 23 MMPs are described, and they are either membrane-anchored or secreted . These enzymes are made up of different domains, modules, and motifs which are the basis for their classification and are important for their substrate
specificity, their localization, and interactions with other macromolecules. All MMPs contain an N-terminal signal peptide which directs the enzymes to the secretory pathway.