Determination of bovine enamel protein by enzyme-linked immuno-adsorbent assay

Determination of enamel protein synthesized by recombined mouse molar tooth germs in organ culture

Epithelial-mesenchymal interaction is a prerequisite for tooth morphogenesis. To study this interaction, inner enamel epithelium and dental papilla mesenchyme of molar tooth germs from a 16.5-day mouse embryo were dissociated enzymatically and cultured alone or after recombination. Characteristic matrix protein synthesized and secreted by recombined tooth germ was determined quantitatively by enzyme-linked immunosorbent assay. The protein was detected in the culture of recombined tooth germ but not of dissociated enamel epithelium alone. The amount of enamel protein increased until 8 days in culture. Morphological differentiation of the recombined epithelial rudiment into ameloblasts and enamel protein production were confirmed.

Immunoblotting and cytochemical characterization of human enamel proteins

Mature enamel proteins (tuft proteins) and fetal enamel proteins were extracted by an homogenizing buffer method, subjected to SDS-PAGE and immunoblotted with a polyclonal antibody raised against the mature enamel proteins. Both fetal and tuft proteins were recognized by this immunoblotting. With the same antibody, immunolocalization of the developing enamel proteins was done on semi-thin-sections of human fetal tissue at the secretory stage, using an immunoperoxidase technique. Specific labelling of the enamel protein matrix was observed. It is concluded that a polyclonal antibody against mature enamel proteins (anti-tuft) can recognize the developing protein matrix at the secretory stage. This suggests that a common antigenic determinant is maintained throughout the course of amelogenesis in human enamel.

Structure and function of enamel gene products

The present paper reviews the main features of amelogenin and enamelin biochemistry, molecular biology, structural and ultrastructural localization, and immunology. It also examines recent studies concerning the origin, chemical characterization, suggested role, and participation of these two major classes of extracellular developing enamel matrix proteins in the complex process of "matrix-mediated" mineralization.

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.

Isolation of two bovine amelogenin peptides and their amino acid sequences

Two peptide fractions of bovine amelogenin having a highly aggregative property to form polymers were purified by chromatography, SDS-polyacrylamide gel electrophoresis, and HPLC. Amino acid sequences of purified peptides were determined by automated Edman degradation. One peptide was found to be composed of 63 amino acid residues having a molecular weight of 7105, and the other of 86 residues having that of 9683. The sequence of the smaller peptide was identical to the C-terminal 63 residues of the amelogenin molecule of 170 residues previously reported, but the larger contained eight residues which are absent in the amelogenin sequence. There is a possibility that the latter peptide might be synthesized independently from mRNA spliced at different positions.

mRNA characterization of human fetal enamel matrix

Preliminary characterization of the human enamel matrix at 16-18 weeks in utero was performed. Using an homogenizing buffer, the proteins were extracted and analysed by gel electrophoresis. Total cellular RNA was isolated and the cell-free mRNA translated. The major component was a 68,000 protein with an enamelin-like amino-acid composition. Other translation products included a 55,000 polypeptide and lower mol. wt components of 26,000, 22,000 and 20,000 size of amelogenin size. It is suggested that high mol. wt component in the enamelin range is the most prevalent at the early stage of human tooth development.