MP-19 (Matrix metalloprotease 19; also MMP-18 and MMP RASI) is a 55-59kD member of the peptidase M10A family of enzymes. It is widely expressed, being secreted by stratum basale keratinocytes, smooth muscle cells, epiphysial cartilage chondrocytes and monocytes/macrophages. MMP-19 has multiple substrates, including components of the basement membrane (type IV collagen; laminin; nidogen), fibronectin, aggrecan plus COMP, and IGFBP3, this latter cleavage resulting in the release of active IGF-I. Studies involving MMP-19 demonstrate an antiangiogenic function. This is attributable to the processing of plasminogen, generating angiostatin-like molecules, and the creation of an environment that promotes the ECM retention of soluble VEGF. Human proMMP-19 is 490aa in length. It contains an autocleavable 9kD propeptide aa19-97 plus a 411aa mature region aa98-508. The mature region contains a Zn catalytic region aa103-256 plus four hemopexin-like domains aa293-508. There are three additional potential isoforms. One shows an 88aa substitution for aa300-508, a second contains a12aa substitution for aa1-298, while a third possesses an alternative start site at Met80. Over aa229-508, human MMP-19 shares 76%aa identity with mouse MMP-19.