Brookes Steven J, Kingswell Nicola J, Barron Martin J, Dixon Michael J, Kirkham Jennifer
Department of Oral Biology, Leeds Dental Institute, University of Leeds, Leeds, UK.
Eur J Oral Sci. 2011 Dec;119 Suppl 1(S1):345-50. doi: 10.1111/j.1600-0722.2011.00869.x.
Enamelin is an extracellular enamel matrix protein essential for normal amelogenesis. After secretion, porcine enamelin is processed to generate several enamelin-degradation products. The cumulative 32-kDa enamelin is the most abundant enamelin present, and various roles for this molecule have been suggested. However, the proteolytic cleavage sites in porcine enamelin that generate the 32-kDa enamelin are not conserved across species, and the 32-kDa enamelin analogue may not be present in all species. To explore this we studied rat enamelin biochemistry using western blotting with anti-peptide IgGs to porcine 32-kDa enamelin and to the putative rat 32-kDa enamelin analogue. The dominant enamelins in secretory-stage rat enamel migrated at around 60-70 kDa. In contrast, the dominant enamelins in secretory-stage porcine enamel migrated at around 32 kDa. In contrast, secretory-stage porcine-enamel enamelins were dominated by the 32-kDa enamelin. Rat enamelin was completely removed from maturation-stage enamel without any accumulation of 32-kDa enamelin. We suggest that a discrete 32-kDa enamelin is not essential for normal amelogenesis in all species, and in pig it may be a processing product of a larger functional enamelin molecule. The pig may be an atypical model in terms of enamelin biochemistry and function, and caution should be exercised when assigning functional roles to the 32-kDa enamelin as a discrete enamel matrix entity.
釉蛋白是正常釉质形成所必需的一种细胞外釉质基质蛋白。分泌后，猪釉蛋白会被加工产生几种釉蛋白降解产物。累积的32 kDa釉蛋白是含量最丰富的釉蛋白，人们已提出该分子具有多种作用。然而，猪釉蛋白中产生32 kDa釉蛋白的蛋白水解切割位点在不同物种间并不保守，而且并非所有物种都存在32 kDa釉蛋白类似物。为了探究这一点，我们使用针对猪32 kDa釉蛋白和假定的大鼠32 kDa釉蛋白类似物的抗肽IgG进行蛋白质印迹法，研究了大鼠釉蛋白的生物化学性质。分泌期大鼠釉质中的主要釉蛋白迁移至约60 - 70 kDa处。相比之下，分泌期猪釉质中的主要釉蛋白迁移至约32 kDa处。相反，分泌期猪釉质中的釉蛋白以32 kDa釉蛋白为主。大鼠釉蛋白在成熟阶段的釉质中完全消失，没有32 kDa釉蛋白的任何积累。我们认为，一个离散的32 kDa釉蛋白并非所有物种正常釉质形成所必需的，在猪中它可能是一个更大的功能性釉蛋白分子的加工产物。就釉蛋白的生物化学性质和功能而言，猪可能是一个非典型模型，在将32 kDa釉蛋白作为一个离散的釉质基质实体赋予功能作用时应谨慎行事。
