The presence and possible functions of the matrix metalloproteinase collagenase activator protein in developing enamel matrix.

The developing enamel matrix contains mostly amelogenins, which are hydrophobic proline-rich proteins. During amelogenesis, the amelogenins are presumably hydrolysed and removed from the enamel. Recently a number of metalloproteinases that may be important in amelogenesis have been identified in zymograms of the developing enamel matrix. In the present study an antibody specific for the matrix metalloproteinase collagenase activator protein (CAP) was characterized and used to identify this metalloproteinase in enamel. Immunoblotting showed that the CAP proteinase was present in the enamel matrix. Immunohistochemistry confirmed that the proteinase is localized in the enamel matrix, most specifically along the dentino-enamel junction. Purified CAP was found to hydrolyse amelogenin protein. Possible functions of the proteinase in the enamel matrix are discussed.