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Mechanism of cross-linking of casein by colloidal calcium phosphae in casein micelles

酪蛋白胶束中胶体磷酸钙交联酪蛋白的机理

基本信息

批准号：
02660146
负责人：
AOKI Takayoshi
金额：
$ 1.22万
依托单位：
Faculty of Agriculture, Kagoshima University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

Calcium and inorganic phosphate are present in excess of their Solubility and interact with casein. Calcium phosphate ity casein micelles, which is associated with casein, is called colloidal calcium phosphate(CCP). Although CCP cross-links caseins through phosphate groups, the mechanism of cross-linking has not yet been elucidated sufficiently. In the present study following results were obtained.A small amount of the 3-P component of human beta-casein and a considerable amount of the 4-P and 5-P components were found in the CCPcross-linked casein separated from artificial casein micelles of whole human casein. CCP-cross-linked casein was formed in artificial casein micelles of tlie 3-P and 4-P components of human beta-casein with kappa-casein. In contrast, no cross-linitage was formed in artificial casein micelles of the 1-P and 2-P coutponeiits. It was concluded that at least three phosphate groups were need fGr cross-linking of casein by CCP.CCP-cross-linked casein taras formed when calcium, phosphate and citrate were added to sodium caseinate solution. This suggested that the submicelle structure and ordered structures of casein were unnecessary for caseins to be cross-linked by CCP.When amino groups of alpha_<s1>-casein were acetylated, citraconilated, orsuccinylated, modified alpha_<s1>-casein was somewhat more hardly cross-linked by CCP than native one.Egg white ribofravin-binding protein is also cross-linked through its phosphate groups by CCP.

钙和无机磷酸盐的存在超过了它们的溶解度，并与酪蛋白相互作用。酪蛋白胶束中的磷酸钙被称为胶体磷酸钙（CCP）.尽管CCP通过磷酸基团交联酪蛋白，但交联的机制尚未得到充分阐明。结果表明，从人β-酪蛋白的人工酪蛋白胶束中分离得到的CCP交联酪蛋白中含有少量的β-酪蛋白的3-P组分和大量的4-P和5-P组分。在人β-酪蛋白的3-P和4-P组分与κ-酪蛋白的人工酪蛋白胶束中形成CCP-交联的酪蛋白。相比之下，在1-P和2-P胶束的人工酪蛋白胶束中没有形成交联。结果表明，CCP对酪蛋白的交联至少需要三个磷酸基团，当在酪蛋白酸钠溶液中加入钙、磷酸盐和柠檬酸盐时，形成CCP交联的酪蛋白Taras。这表明CCP交联酪蛋白不需要酪蛋白的亚胶束结构和有序结构，当α_<s1>-酪蛋白的氨基被乙酰化、柠康酸化或琥珀酰化时，CCP对修饰的α_<s1>-酪蛋白的交联作用比天然酪蛋白稍弱，卵白白色核蛋白结合蛋白也可通过磷酸基团被CCP交联。