详细描述：
Matrix metalloproteinases are a family of zinc and calcium-dependent endopeptidases that break down extracellular matrix proteins. The MMP-9 is secreted as a 92 kDa zymogen. Cleavage of ProMMP-9 results in the active enzyme, having a molecular weight of approximately 82 kDa. MMP-9 is composed of the following domains: a gelatin-binding domain consisting of three fibronectin type II units, a catalytic domain containing the zinc-binding site, a proline-rich type V collagen-homologous domain and a hemopexin-like domain. MMP-9 is produced by the several cell types: monocytes, macrophages, neutrophils, keratinocytes, fibroblasts, osteoclasts and endothelial cells. MMP-9 is involved in inflammatory responses, tissue remodeling, wound healing, tumor growth and metastasis. MMP-9 may also play an important part in local proteolysis of the extracellular matrix and in leukocyte migration, as well as in bone osteoclastic resorption. MMP-9 cleaves type IV and type V collagens into large C-terminal three quarter fragments and shorter N-terminal one quarter fragments. MMP-9 can also degrade fibronectin but not laminin or Pz-peptide. MMP-9 defects may be a cause of susceptibility to intervertebral disc disease (IDD), also known as lumbar disk herniation (LDH).
