Nucleation and inhibition of hydroxyapatite formation by mineralized tissue proteins
Nucleation and inhibition of hydroxyapatite formation by mineralized tissue proteins
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DOI：
10.1042/bj3170059
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发表时间：
1996-07-01
影响因子：
4.1
通讯作者：
Goldberg, HA
中科院分区：
文献类型：
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作者：
Hunter, GK;Hauschka, PV;Goldberg, HA
在矿化组织中发现的许多蛋白质被认为是矿化过程的调节因子，要么是羟基磷灰石(HA)形成的核因子，要么是HA的抑制因子。我们研究了不同浓度的骨蛋白[骨钙素(OC)、骨桥蛋白(OPN)、骨联素(ON)和骨涎蛋白(BSP)]、牙本质[磷蛋白(DPP)]和钙化软骨[软骨钙蛋白(CC)]的HA成核和抑制特性。用稳定的琼脂糖凝胶体系研究了亚阈值[Ca]x[PO4]产物中HA的成核作用。BSP和DPP在最低浓度分别为0.3mU g/m l(9 NM)和10 mU g/m l(67 NM)时具有成核活性，OC、OPN、ON和CC在浓度高达100 mU g/m l时均无成核活性。OPN对HA形成有较强的抑制作用[IC50=0.32 mU/ml(0.01 mU M)]，而OC的抑制作用较弱[IC50=6.1 mU g/ml(1.1 mU M)]，BSP、ON和CC在浓度达10 mU g/ml时均缺乏抑制活性，OPN对HA形成的抑制作用主要是抑制晶体生长，而OC则延缓成核。这些发现与BSP和DPP可能分别在骨和牙本质中起矿化作用的观点是一致的。OPN似乎是矿化的组织蛋白，最有可能通过阻止高过饱和度组织液中的相分离来抑制HA的形成。
Many proteins found in mineralized tissues have been proposed to function as regulators of the mineralization process, either as nucleators or inhibitors of hydroxyapatite (HA) formation. We have studied the HA-nucleating and HA-inhibiting properties of proteins from bone [osteocalcin (OC), osteopontin (OPN), osteonectin (ON) and bone sialoprotein (BSP)], dentine [phosphophoryn (DPP)] and calcified cartilage [chondrocalcin (CC)] over a wide range of concentrations. Nucleation of HA was studied with a steady-state agarose gel system at sub-threshold [Ca] x [PO4] product. BSP and DPP exhibited nucleation activity at minimum concentrations of 0.3 mu g/ml (9 nM) and 10 mu g/ml (67 nM) respectively, OC, OPN, ON and CC all lacked nucleation activity at concentrations up to 100 mu g/ml. Inhibition of HA formation de novo was studied with calcium phosphate solutions buffered by autotitration. OPN was found to be a potent inhibitor of HA formation [IC50 = 0.32 mu g/ml (0.01 mu M)] whereas OC was of lower potency [IC50 = 6.1 mu g/ml (1.1 mu M)]; BSP, ON and CC all lacked inhibitory activity at concentrations up to 10 mu g/ml. The effect of OPN on HA formation de novo is mainly to inhibit crystal growth, whereas OC delays nucleation. These findings are consistent with the view that BSP and DPP may play roles in the initiation of mineralization in bone and dentine respectively. OPN seems to be the mineralized tissue protein most likely to function in the inhibition of HA formation, possibly by preventing phase separation in tissue fluids of high supersaturation.