Localization of enamel proteins : an electron microscopic immunocytochemical study using antibodies against synthetic peptides.

用猪牙釉质蛋白合成肽段抗体对猪和大鼠未成熟牙釉质进行了免疫化学和免疫细胞化学研究。研究结果如下：1.最初分泌的釉原蛋白（25 kDa釉原蛋白）优先定位于未成熟釉质的表层，并降解产生20 kDa和其他分子量较低的釉原蛋白，这些蛋白存在于未成熟釉质的深层. 20 kDa釉原蛋白降解产生的6-7 kDa釉原蛋白（含25 kDa釉原蛋白1-45位残基的N端片段）在表层很少发现，主要定位于深层，尤其是在未成熟釉质的杆鞘中. 89 kDa的釉蛋白定位于杆和杆间釉质后，其分泌的成釉细胞和降解速度比25 kDa的釉原蛋白。89 kDa釉蛋白降解产生的N端小分子肽可能集中在视杆鞘中.视杆鞘主要由一类新的釉蛋白家族组成，即视杆鞘蛋白，不同于釉原蛋白或釉蛋白。然后将降解的釉原蛋白和釉蛋白添加到杆鞘中。最初分泌的杆鞘蛋白的分子量估计为30-40 kDa，并且可能比25 kDa的釉原蛋白降解得更快。大鼠切牙和磨牙的未成熟釉质中没有杆状鞘，表明大鼠的釉质发生可能与猪和人的釉质发生有些不同。32 kDa的nonamelogenin蛋白可能是140 kDa和/或89 kDa蛋白的降解产物，这两种蛋白都存在于杆和杆间釉质中，并且可能在釉质形成的初始钙化和晶体生长调节中发挥重要作用。

Immature enamel of the pig and the rat were investigated immunochemically and immunocytochemically using antibodies against synthetic peptide fragments of porcine enamel proteins. The results are summarized as follows.1. Originally secreted amelogenin, the 25 kDa amelogenin, is preferentially localized in the surface layer of immature enamel and is degraded to produce 20 kDa and other lower molecular weigh amelogenins which are found in deeper layer of the immature enamel.2. The 6-7 kDa amelogenin ( N-terminal segment containing residues 1-45 of the 25 kDa amelogenin) produced by degradation of the 20 kDa amelogenins were rarely found in surface layer and were predominantly localized in deep layer, especially in the rod sheath of immature enamel.3. The 89 kDa enamelin is localized in rod and interrod enamel just after its secretion from the ameloblast and is degraded faster than the 25 kDa amelogenin. Some N-terminal low molecular weight peptides produced by degradation of the 89 kDa enamelin may be concentrated in the rod sheaths.4. The rod sheaths are primarily composed of a new category of enamel protein family, the rod sheath proteins, different from the amelogenins or enamelins. Degraded amelogenins and enamelins are then added to the rod sheaths. Molecular weights of originally secreted rod sheath proteins are estimated 30-40 kDa and may be degraded faster than the 25 kDa amelogenin.5. The rod sheaths are absent from the immature enamel of rat incisors and molars, indicating the amelogenesis of the rat may somewhat differ from that of pig and man.6. The 32 kDa nonamelogenin protein is likely to be a degradation product of the 140 kDa and/or 89 kDa proteins, both of which are present in the rod and interrod enamel and may play a significant role in the initial calcification and crystal growth regulation in the amelogenesis.