INTRAMITOCHONDRIAL STORAGE OF STABLE AMORPHOUS CALCIUM PHOSPHATE *
INTRAMITOCHONDRIAL STORAGE OF STABLE AMORPHOUS CALCIUM PHOSPHATE *
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稳定的无定形磷酸钙的线粒体内储存 *
DOI：
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发表时间：
1978
影响因子：
5.2
通讯作者：
A. S. Posner
中科院分区：
文献类型：
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作者：
A. S. Posner
来自不同动物物种的多种细胞的线粒体可以积累稳定的磷酸钙沉积，这些沉积对X射线和电子衍射来说是无定形的。与羟基磷灰石(HA)晶体相反的无定形颗粒的出现引起了人们的注意，因为稳定的生物磷酸钙通常以结晶态存在。在这一点上，在骨形成过程中沉积的第一种矿物是无定形状态，它在短时间内转化为结晶度不高的含C0的HA。线粒体内无定形磷酸钙(ACP)的形成需要镁和三磷酸腺苷(ATP)的存在。在溶液中，当镁和三磷酸腺苷一起用于延迟无定形磷酸钙浆液向透明质酸的转化时，观察到了协同效应。转化延迟的时间是单独使用三磷酸腺苷或镁的10倍以上(两者都在线粒体中的浓度)，直到检测不到溶液三磷酸腺苷时才开始。镁的作用是降低ATP的水解率。此外，还发现三磷酸腺苷可以防止亚稳态磷酸钙溶液中HA的形成。结果表明，ATP通过毒化异核HA生长部位和/或在胚胎HA核达到临界大小之前毒化其生长，使其溶解，从而阻止稳定的HA晶体的形成，从而稳定了ACP。通过调节镁、三磷酸腺苷和三磷酸腺苷酶水平。细胞可以根据需要储存或利用ACP颗粒。用X射线衍射法测定青蟹肝胰腺胞质ACP的径向分布函数(RDF)，与人工合成的ACP的径向分布函数相似，表明两者都只有-9.5A的短程原子有序，最长的DIm En~1On。~在合成的ACP中，簇的组成是Ca，(PO，)，在RDF中观察到的微小差异(图1)是由于蓝蟹簇中的Mg~(2+)取代Ca~(2+)而导致的结构扭曲。过去的RDF工作表明，在电子显微镜下被视为3001000-A球状的酸性磷酸酶颗粒，由位于间隙中的15%-20%的水随机填充的磷酸钙离子簇组成。6我们可以推测，胚胎HA核中的镁替代可能会导致如此严重的扭曲，从而阻止生长，诱导溶解，防止HA的形成。
The mitochondria of many types of cells from a variety of animal species can accumulate stable deposits of calcium phosphate that are amorphous to x-ray and electron diffraction. The appearance of amorphous granules as opposed to crystals of hydroxyapatite (HA) attracted attention, since stable biological calcium phosphates were generally found in the crystalline state. In this regard, the first mineral deposited in bone formation is in an amorphous phase, which transforms in a short time to a poorly crystallized, C0,-containing HA.' The presence of Mg and ATP is needed for the formation of intramitochondrial amorphous calcium phosphate (ACP).2 An in v i t ro , synergistic effect has been observed when Mg and ATP are used together in solution to delay the conversion of a slurry of ACP to HA., Conversion, delayed more than 10 times as long as with either ATP or Mg alone (both at the concentrations found in mitochondria), did not begin until solution ATP was undetectable. The effect of Mg is to decrease the ATP hydrolysis rate. ATP was also found to prevent HA formation from metastable calcium phosphate solutions. It was concluded that ATP stabilized ACP by poisoning heteronuclear H A growth sites and/or by poisoning the growth of embryonic HA nuclei before their critical size is reached, causing them to dissolve, thus preventing stable H A crystal formation. By regulating the Mg, ATP, and ATPase levels. the cell can store or utilize the ACP granules as the need arises. The radial distribution function (RDF) calculated from x-ray diffraction from cytoplasmic ACP of the hepatopancreas of the blue crab is similar to that of synthetic ACP, indicating that both have only short-range atomic order in the form of neutral ion clusters -9.5 A in the longest d i m e n ~ i o n . ~ In synthetic ACP the cluster composition is Ca,(PO,), and the minor differences observed in RDFs (FIGURE 1) are due to structural distortions resulting from the substitution of Mg2+ for Ca2+ in the blue crab cluster.g ATP had no effect on the ACP cluster. Past RDF work suggested that the ACP granules, seen in the electron microscope as 3001000-A spheres, consist of a random packing of the calcium phosphate ion cluster with 15%-20% water located in the interstices.6 We can postulate that Mg substitution in embryonic HA nuclei may induce so much distortion that growth is prevented, solution is induced, and HA formation is prevented.