Purification, characterization, and biosynthesis of bovine enamelins

Enamelins were extracted from developing bovine enamel with 0.5 M EDTA, 4 M guanidine HCl, and purified by DEAE-Sephacel, Sephacryl S-200, and high-performance gel filtration chromatography. Four distinct enamelins having molecular weights of 70, 45, 30, and 28 K daltons were isolated. Their amino acid compositions were found to be rich in Pro, Glu, Gly, and Asp. Low molecular weight enamelins (45, 30, and 28 K) were more abundant in Pro, Gly, and Phe. Two-dimensional electrophoretic pattern of enamelins revealed several spots that immunoreacted to monoclonal anti-enamelin antibody raised in mice. Enamelins were found to be comprised of heterogeneous proteins as well as amelogenins. Biosynthesis of enamelins was investigated by incubating the bovine ameloblast cell layer, and several radioactive enamelins were identified by the use of two-dimensional electrophoresis. The data in this study suggest that enamelins were synthesized by the ameloblasts.