Llano E, Pendás A M, Knäuper V, Sorsa T, Salo T, Salido E, Murphy G, Simmer J P, Bartlett J D, López-Otín C
Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Oviedo, 33006 Oviedo, Spain.
Biochemistry. 1997 Dec 9;36(49):15101-8. doi: 10.1021/bi972120y.
A cDNA encoding a new human matrix metalloproteinase (MMP) has been cloned from RNA prepared from odontoblastic cells. The open reading frame of the cloned cDNA codes for a polypeptide of 483 amino acids and is extensively similar to the sequence of recently described porcine enamelysin, suggesting that the isolated cDNA codes for the human homologue of this enzyme. Human enamelysin (MMP-20) has a domain organization similar to other MMPs, including a signal peptide, a prodomain with the conserved motif PRCGVPD involved in maintaining enzyme latency, a catalytic domain with a Zn-binding site, and a COOH-terminal fragment similar to the sequence of hemopexin. The calculated molecular mass of human enamelysin is about 54 kDa, which is similar to that of collagenases or stromelysins. However, this human MMP lacks a series of structural features distinctive of these subfamilies of MMPs. The full-length human enamelysin cDNA has been expressed in Escherichia coli, and the purified and refolded recombinant protein is able to degrade synthetic peptides used as substrates of MMPs, confirming that human enamelysin belongs to this family of proteases. Furthermore, the recombinant human enamelysin is able to degrade amelogenin, the major protein component of the enamel matrix. On the basis of its degrading activity on amelogenin, and its highly restricted expression to dental tissues, we suggest that human enamelysin plays a central role in the process of tooth enamel formation. Finally, we have found that the human enamelysin gene (MMP-20) maps to chromosome 11q22, clustered to at least seven other members of the MMP gene family.
已从成牙本质细胞制备的RNA中克隆出一种编码新型人类基质金属蛋白酶（MMP）的cDNA。克隆的cDNA的开放阅读框编码一个483个氨基酸的多肽，与最近描述的猪釉质溶解蛋白的序列高度相似，这表明分离出的cDNA编码该酶的人类同源物。人类釉质溶解蛋白（MMP - 20）具有与其他MMP相似的结构域组织，包括一个信号肽、一个带有参与维持酶潜伏性的保守基序PRCGVPD的前结构域、一个带有锌结合位点的催化结构域以及一个与血红素结合蛋白序列相似的COOH末端片段。计算得出的人类釉质溶解蛋白的分子量约为54 kDa，与胶原酶或基质溶解素的分子量相似。然而，这种人类MMP缺乏这些MMP亚家族特有的一系列结构特征。全长人类釉质溶解蛋白cDNA已在大肠杆菌中表达，纯化并重新折叠的重组蛋白能够降解用作MMP底物的合成肽，证实人类釉质溶解蛋白属于这个蛋白酶家族。此外，重组人类釉质溶解蛋白能够降解釉原蛋白，即釉质基质的主要蛋白质成分。基于其对釉原蛋白的降解活性以及在牙齿组织中的高度特异性表达，我们认为人类釉质溶解蛋白在牙釉质形成过程中起核心作用。最后，我们发现人类釉质溶解蛋白基因（MMP - 20）定位于染色体11q22，与MMP基因家族的至少其他七个成员聚集在一起。
