Description
Introduction: Matrix metalloproteinases (MMPs), also called matrixins, constitute a family of zinc and calcium-dependent endopeptidases that function in the breakdown of extracellular matrix and in the processing of a variety of biological molecules. They play an important role in many normal physiological processes such as embryonic development, morphogenesis, reproduction and tissue remodeling. They also participate in many pathological processes such as arthritis, cancer and cardiovascular disease. While the amounts of newly synthesized MMPs are regulated mainly at the levels of transcription, the proteolytic activities of existing MMPs are controlled through both the activation of proenzymes or zymogens and the inhibition of active enzymes by endogenous inhibitors such as alpha2-macroglobulins and tissue inhibitors of metalloproteinases (TIMPs). MMP-2 (gelatinase A) is primarily expressed in mesenchymal cells (mainly fibroblasts) during development and tissue regeneration. It is highly expressed in stromal cells surrounding the invading front of metastasizing tumors and associated with many connective tissue cells as well as neutrophils, macrophages and monocytes. It is required for the switch to the angiogenic phenotype in a tumor model and its levels are elevated in tumor endothelium and in urine of patients with a variety of cancers. Together with MMP-9 (gelatinase B), it degrades type IV collagen, the major component of basement membranes and gelatin (denatured collagen). It can also degrade other types of collagens (V, VII and X) as well as elastin and fibronectin. It processes many other molecules, modulating their functions in different pathways. Human and mouse MMP-2 are secreted as 72 kDa proenzymes of 631 and 662 amino acids, respectively. The removal of the pro domain can be initiated by membrane-type MMPs or by serine proteases such as thrombin and activated protein C. The resulting mature and active enzyme consists of a catalytic domain, which is interrupted by three contiguous fibronectin type II-like domains, and a C-terminal, hemopexin-like domain. TIMPs inhibit active MMP-2 through tight, but non-covalent binding of their N-terminal domains to the catalytic domain of MMP-2 in a 1:1 stoichiometry. In addition, TIMP-2 can bind to the proenzyme through interaction between the C-terminal domains of both proteins.
Principle of the Assay: This assay employs the quantitative sandwich enzyme immunoassay technique. Antibody specific for MMP-2 has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any MMP-2 present is bound by the immobilized antibody. After removing any unbound substances, a biotin-conjugated antibody specific for MMP-2 is added to the wells. After washing, avidin conjugated Horseradish Peroxidase (HRP) is added to the wells. Following a wash to remove any unbound avidin-enzyme reagent, a substrate solution is added to the wells and color develops in proportion to the amount of MMP-2 bound in the initial step. The color development is stopped and the intensity of the color is measured