The matrix metalloproteinases (MMPs) are a family of at least eighteen secreted and membrane bound zinc endopeptidases. Collectively, these enzymes can degrade all the components of the extracellular matrix, including fibrillar and non fibrillar collagens, fibronectin, laminin and basement membrane glycoproteins. In general, a signal peptide, a propeptide, and a catalytic domain containing the highly conserved zinc binding site characterizes the structure of the MMPs. In addition, fibronectin like repeats, a hinge region, and a C terminal hemopexin like domain allow categorization of MMPs into the collagenase, gelatinase, stomelysin and membrane type MMP subfamilies. All MMPs are synthesized as proenzymes, and most of them are secreted from the cells as proenzymes. Thus, the activation of these proenzymes is a critical step that leads to extracellular matrix breakdown. MMPs are considered to play an important role in wound healing, apoptosis, bone elongation, embryo development, uterine involution, angiogenesis and tissue remodeling, and in diseases such as multiple sclerosis, Alzheimer's, malignant gliomas, lupus, arthritis, periodontis, glumerulonephritis, atherosclerosis, tissue ulceration, and in cancer cell invasion and metastasis.
MMP16 induces the activation of pro gelatinase A (MMP2). It was identified as a membrane bound Metalloproteinase in normal and tumor cell lines. MMP16 is similar to the other MtMMPs; it contains a furin cleavage site, is membrane bound, and contains a cytoplasmic tail (MT4MMP lacks the tail, and may not be intercalated into the membrane). MMP16 is also known to be "shed" from the membrane in a soluble form. MT1MMP is known to function in activating a number of MMPs, chiefly MMP2, but that role has not been well described for the other MTMMPs. MMP16 has been reported to be elevated in several tumor cell lines, and is constituitively produced by some normal cell lines.