Mechanistic Understanding of the Maturation of Developing Enamel. Plausible Interactions among Crystals, Matrix Proteins and Proteases.

Abstract

The present study investigated the crystal-protein -protease interaction and the resulting effects on mineral precipitation under experimental conditions assimilated to those found in the en amel fluid surrounding the secretory enamel mineral . Materials used were synthetic hydroxyapatite , enamel proteins isolated from porcine secretory enamel , and trypsin as a prototype of enamel proteases . Two anti-peptide sera, reactive with the C-terminal epitope (s) of amelogenins , were used to assign the amelogenins and degraded products. It was verified that trypsin initially cleaved the hydrophilic domain of the secreted amelogenins in the liquid phase because the corresponding domain is likely exposed on protein surface.

Dental Fluorosis: Chemistry and Biology

“…Additional protection of the putative cleavage sites against proteases may occur by possible changes in molecular conformation of substrate proteins upon protein-crystal associations (Aoba et al ., 1989b). In fact, the majority of the secreted enamel proteins, including the intact amelogenins, have adsorption affinity for apatite crystals (Aoba et al ., 1987a), and, experimentally, the proteins residing on apatite crystals were proven to be more resistant to enzymatic cleavages, as compared with the hydrolytic rates of protein degradation in the absence of crystals (Aoba, 1994; MoradianOldak et al ., 1998;Yamazaki et al ., 2000). Importantly, increasing fluoride uptake by enamel tissue promotes fluoridation of enamel crystals ( i.e.…”