The enzyme Gamma -glutamyl transpeptidase, GGT, is found in cells which are active in secretory and resorptive processes. It has been found to be strongly associated with cells which possess a brush border. The cells of the enamel organ, especially the ameloblasts, undergo profound changes in their life cycle. They begin as relatively undifferentiated cells, become active secretory cells and later during the stage of maturation they become active resorptive cells. Since enamel proteins contain a high proportion (about 20%) of the amino acid, glutamic acid, the developing tooth could serve as an excellent model for studying developmentally regulated enzyme activity of GGT. Thus far there is only one report showing that GGT is present in developing teeth (Lindskog and Hammarstrom, 1981). It was stated that activity was only present during the stage of matrix production (not before) and that stronger activity was present in the maturation stage. Preliminary studies in this laboratory using immunohistochemical staining and a sensitive fluorometric assay have shown that prior to the synthesis of enamel matrix GGT is present and active in the enamel organ of newborn mouse molars. This proposal is designed to study the localization and activity of GGT in the enamel organ at various stages of development. It is hoped that through a study such as this more will be learned of the function of this enzyme and more specifically of its role in the formation and maturation of enamel. Since GGT is a membrane bound enzyme it may also prove to be a convenient marker enzyme to study the dynamics of membrane flow during enamel secretion and during the maturation stage when ameloblasts are modulating.
