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Inhibitory activity of bovine milk osteopontin and its fragments on the formation of calcium phosphate precipitates

机译:牛骨桥蛋白及其片段对磷酸钙沉淀物形成的抑制作用

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Osteopontin (OPN) is an acidic phosphorylated glyco-protein found in many tissues and physiological fluids. OPN is known to possess multiple biological functions including bone remodeling, cell adhesion, cellular transformation and immunological mediation; these functions have been extensively reviewed (Butler et al. 1996; Sodek et al. 2000). In mammary gland, the involvement of OPN in mammary differentiation and involution has been proposed (Rittling & Novick, 1997; Nemir et al. 2000). The biological significance of OPN in mammary secretion remains unclear, however, Nagatomo et al. (2004) predicted a contribution of OPN in human milk to the immunological development of breast-fed infants. They observed an increase of OPN concentration as lactation proceeded, and it was not unusual to find the concentration of OPN in human milk exceeding in 1 g/l. In contrast, the abundance of OPN in bovine mammary secretion is recognized at the early stage of lactation rather than in matured milk, and the concentration of OPN in mature bovine milk is estimated to be about 10 mg/l (Kumura et al. 2004). Thus, the level of OPN is much higher in human milk than in bovine milk. Christensen et al. (2005) reported the post-translational modification of 36 phosphorylation sites in human milk OPN while Sorensen et al. (1995) reported that mature bovine milk OPN consisted of 262 amino acids and was phosphorylated at 27 serine residues and one threonine residue. Considering its availability, bovine OPN is an attractive source for OPN. In fact, OPN can be prepared easily from milk or whey (Bayless et al. 1997; Azuma et a). 2006). When intact OPN is required, acid whey should be used because OPN is susceptible to chymosin (Kumura et al. 2004). Traditional cheese making practice leads to fragmentation of OPN due to chymosin and results in release of a variety of phosphorylated peptides in cheese whey since phospholylated amino acid residues are distributed throughout the OPN molecule. Among the phosphorylated peptides derived from milk, casein phosphopeptide (CPP), which could be obtained by exposure of casein to intestinal digestion, is well known and possesses a high calcium binding capacity that prevents the precipitation of calcium phosphate salts. CPP is regarded as a functional food ingredient that increases the soluble intraluminal calcium availability for absorption across the mucosa (Naito, 1986; Kitts & Yuan, 1992) and is authorized as a food for specified uses (FOSHU) by the Japanese Ministry of Health, Labour and Welfare. In this study, we observed inhibitory activity of OPN and its fragment on the formation of calcium phosphate precipitates. Comparative study of its activity with CPP was also conducted, and the sequence in OPN molecule responsible for its activity is discussed.
机译:骨桥蛋白(OPN)是一种酸性磷酸化糖蛋白,存在于许多组织和生理液中。已知OPN具有多种生物学功能,包括骨骼重塑,细胞粘附,细胞转化和免疫介导。这些功能已得到广泛的审查(Butler等,1996; Sodek等,2000)。在乳腺中,已经提出了OPN参与乳腺分化和内卷化(Rittling&Novick,1997; Ne​​mir等人,2000)。 OPN在乳腺分泌中的生物学意义尚不清楚,但是,Nagatomo等。 (2004)预测人乳中OPN对母乳喂养婴儿免疫学发展的贡献。他们观察到泌乳过程中OPN浓度增加,发现母乳中OPN浓度超过1 g / l并不罕见。相反,在泌乳初期而不是在成熟的牛奶中就可以发现牛乳腺分泌的大量OPN,而成熟牛乳中OPN的浓度估计约为10 mg / l(Kumura等,2004)。 。因此,人乳中的OPN水平比牛乳中的OPN水平高得多。 Christensen等。 (2005年)报道了人乳OPN中36个磷酸化位点的翻译后修饰,而Sorensen等人(2005年)报道。 (1995)报道成熟的牛乳OPN由262个氨基酸组成,在27个丝氨酸残基和1个苏氨酸残基处被磷酸化。考虑到其可用性,牛OPN是OPN的诱人来源。实际上,OPN可以很容易地从牛奶或乳清中制备(Bayless等,1997; Azuma等)。 2006)。当需要完整的OPN时,应使用酸性乳清,因为OPN对凝乳酶敏感(Kumura等,2004)。传统的干酪生产实践由于凝乳酶导致OPN断裂,并且由于磷酸化的氨基酸残基分布在整个OPN分子中,导致干酪乳清中多种磷酸化肽的释放。在酪蛋白衍生的磷酸化肽中,酪蛋白磷酸肽(CPP)可以通过酪蛋白暴露于肠道消化而获得,它具有很高的钙结合能力,可防止磷酸钙盐沉淀。 CPP被认为是一种功能性食品成分,可以增加可溶腔内钙在整个粘膜中的吸收(Naito,1986; Kitts&Yuan,1992),并且被日本厚生省批准为特定用途食品(FOSHU),劳动和福利。在这项研究中,我们观察到OPN及其片段对磷酸钙沉淀物形成的抑制活性。还对其与CPP的活性进行了比较研究,并讨论了OPN分子中负责其活性的序列。

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