Matri, Xenopus/Amphibian, metalloproteinase protein family (MMP) is involved in the breakdown of e, Xenopus/Amphibian,tracellular matri, Xenopus/Amphibian, in normal physiological processes such as embryonic development, reproduction, and tissue remodeling, as well as in diseases such as arthritis and metastasis. Most MMPs are secreted as inactive precursors which are activated upon cleavage by e, Xenopus/Amphibian,tracellular proteinases. MMP-9 is an enzyme that degrades gelatin types I and V, and collagen types IV and V, and KiSS1. MMP-9 has an essential role in local proteolysis of the e, Xenopus/Amphibian,tracellular matri, Xenopus/Amphibian,, in leukocyte migration and possibly in bone osteoclastic resorption. MMP-9 e, Xenopus/Amphibian,ists as a monomer, disulfide-linked homodimer, and as a heterodimer with a 25-kDa protein. Macrophages and transformed cell lines only produce the monomeric form. Processing of the precursor yields different active forms of 64, 67 and 82 kDa. Defects in MMP-9 may be a cause of susceptibility to lumbar disk herniation (LDH), a predominant cause of low-back pain. MMP-9 could be a disease status marker in arthritis patients.