In a model of explant growth in vitro using corneal epithelium, Matrix Metalloproteinase (MMP) 2 expression correlates with an initial degradation of the original basement membrane. Reformation of basement membrane in culture was dependent on an initial upregulation followed by a downregulation of MMP-9, in contrast to the constant expression of MMP-2. This is not evidence that MMP-2 and MMP-9 directly cleave perlecan protein in vivo but shows that the proteins clearly modulate some factor in maturation of basement membrane. Another family of metalloproteases, the Bone Morphogenetic Protein 1/Tolloid-like family, releases the c-terminal endorepellin domain of the perlecan core protein. The laminin-like globular domain contains the active motif of endorepellin, and is unable to be cleaved by cells expressing mutant and inactive forms of the BMP-1 proteins. Furthermore, the critical residue necessary for this cleavage to take place was localized to Asp4197. This proteolytic process may have significance in disease as a corresponding fragment was found in the urine of patients suffering end-stage renal failure and in the amniotic fluid of pregnant women who have undergone premature rupture of the membrane.