Enamel is initially secreted as a protein matrix. The largest fraction of the protein matrix consists of amelogenins, which are selectively removed from the enamel as maturation progresses. Hydrolysis of the amelogenins by one or more enamel proteinase(s) is a likely mechanism for the progressive removal of amelogenins from the enamel matrix. Preliminary studies of this proposal suggest that six or more proteinases are present in developing enamel. The long-term objective of this proposal is to investigate these proteinases found in developing dental enamel.
The specific aims of this proposal include the following: (1) to isolate and purify proteinases found in the extracellular matrix of developing bovine enamel; (2) to characterize these proteinases by determining specificity profiles for substrates and inhibitors, pH optima and thermal stabilities: (3) to determine which proteinases hydrolyze amelogenins and to determine the specific cleavage sites using the purified 25,000 MW amelogenin as a substrate; (4) to prepare polyclonal antibodies against the enamel proteinases. Careful purification and characterization of the enamel proteinases will be completed to allow further studies on the function of the various proteinases in developing enamel. Purified amelogenin will then be used as a substrate. The hydrolysis products will be compared to proteins and peptides known to exist in vivo, which are likely hydrolysis products of high molecular weight amelogenin. The preparation of polyclonal antibodies against the isolated enamel proteinases will allow further studies such as the immunohistochemical localization of the various enamel proteinases in the enamel matrix and in the enamel organ. Investigation of the proteinases present in developing enamel will lead to better understanding of the processes involved in amelogenesis. Understanding the function of enamel formation such as amelogenesis imperfecta and enamel fluorosis, which have retained enamel protein with subsequent poor mineralization.
