Physicochemical characterization of casein phosphopeptide-amorphous calcium phosphate nanocomplexes
Physicochemical characterization of casein phosphopeptide-amorphous calcium phosphate nanocomplexes
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DOI：
10.1074/jbc.m413504200
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发表时间：
2005-04-15
影响因子：
4.8
通讯作者：
Reynolds, EC
中科院分区：
文献类型：
--
作者：
Cross, KJ;Huq, NL;Reynolds, EC
牛奶酪蛋白稳定钙和磷酸盐离子，使它们为新生儿所用。酪蛋白的胰蛋白酶消化从其极性n端区域产生含有磷酸化丝氨酸残基簇的磷酸肽。这些磷酸丝氨酸簇被假设为酪蛋白和磷酸钙之间的相互作用，导致酪蛋白胶束的形成。酪蛋白磷酸肽通过形成复合物来稳定钙离子和磷酸离子。这些复合物中的磷酸钙在生物上可用于肠道吸收和牙釉质表面下病变的再矿化。我们使用一系列的物理化学技术，包括x射线粉末衍射、扫描电子显微镜、透射电子显微镜和平衡结合分析，研究了酪蛋白磷酸肽与磷酸钙形成的复合物的结构。通过x射线粉末衍射和选择区域衍射两种独立的方法证实了磷酸钙相的无定形性质。在溶液中，碱性无定形磷酸钙相的离子活性产物是唯一与pH无关的结合磷酸函数的离子产物，与酪蛋白磷酸肽稳定的碱性无定形磷酸钙相一致。利用酪蛋白磷酸化肽的合成同源物和类似物对钙和磷酸钙结合的详细研究表明，尽管完全磷酸化的seryl簇基序是钙和磷酸钙相互作用的关键，但其他因素也很重要。特别是，肽的钙结合和磷酸钙稳定受到肽净电荷、长度和序列的影响。
Milk caseins stabilize calcium and phosphate ions and make them available to the neonate. Tryptic digestion of the caseins yields phosphopeptides from their polar N-terminal regions that contain clusters of phosphorylated seryl residues. These phosphoseryl clusters have been hypothesized to be responsible for the interaction between the caseins and calcium phosphate that lead to the formation of casein micelles. The casein phosphopeptides stabilize calcium and phosphate ions through the formation of complexes. The calcium phosphate in these complexes is biologically available for intestinal absorption and remineralization of subsurface lesions in tooth enamel. We have studied the structure of the complexes formed by the casein phosphopeptides with calcium phosphate using a range of physicochemical techniques including x-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, and equilibrium binding analyses. The amorphous nature of the calcium phosphate phase was confirmed by two independent methods: x-ray powder diffraction and selected area diffraction. In solution, the ion activity product of a basic amorphous calcium phosphate phase was the only ion product that was a function of bound phosphate independent of pH, consistent with basic amorphous calcium phosphate being the phase stabilized by the casein phosphopeptides. Detailed investigations of calcium and calcium phosphate binding using a library of synthetic homologues and analogues of the casein phosphopeptides have revealed that although the fully phosphorylated seryl-cluster motif is pivotal for the interaction with calcium and phosphate, other factors are also important. In particular, calcium binding and calcium phosphate stabilization by the peptides was influenced by peptide net charge, length, and sequence.