Matrix metalloproteinase (MMP) family proteins are involved in the breakdown of extracellular matrix, and have been recognized as potential targets for a variety of pathologies. Matrix metallopeptidase 9 (MMP-9), also known as 92 kDa type IV collagenase, 92 kDa gelatinase or gelatinase B, is the mostly studied MMP, due to its fundamental roles in cancer biology, autoimmune disease, and other conditions.MMP-9 is a metalloenzyme, composed of a pro-domain, a gelatin binding domain, a catalytic domain, a proline rich linker region, and a carboxyl terminal hemopexin like domain. This enzyme degrades various substrates including gelatin, collagen types IV / V, and elastin. MMP-9 Inhibitor Screening Kit provides a quick and sensitive way for screening, studying and characterizing potential inhibitors of MMP-9. In this assay, MMP-9 hydrolyzes a FRET-based MMP-9 substrate and releases the quenched fluorescent group Mca, which can be detected fluorometrically at Ex/Em=325/393 nm.