磷酸肽的钙结合机制及抑制磷酸钙结晶的效果

Mechanism of binding Ca^(2+) and the effect of inhibiting calcium phosphate crystal formation of phosphopeptide

探讨源于鲤鱼卵肽(carp egg peptide,CEP)的磷酸肽(isolated phosphopeptide,IPP)的钙结合机制及其抑制磷酸钙结晶的效果。通过质谱和红外光谱解析IPP结合钙的位点,通过红外光谱和圆二色谱分析IPP结合钙前后的空间结构变化,并通过电镜观察IPP抑制磷酸钙结晶的效果。结果表明,磷酸基团是钙离子的优先结合部位,1分子IPP能结合4个钙离子,羧酸基团未参与钙离子的结合。IPP在生理p H下无论是否结合钙离子均未形成有序的空间二级结构,完全以无序状态存在。在磷酸钙过饱和溶液中,IPP能够与磷酸根离子竞争与钙离子的结合,并吸附到晶核表面,抑制其聚集成结晶。IPP是通过磷酸基团与钙结合,并能有效抑制磷酸钙结晶。

To investigate the mechanism of binding Ca^(2+) and the effect of inhibiting calcium phosphate crystals formation of isolated phosphopeptide( IPP) derived from carp egg peptide( CEP). The Ca^(2+) binding sites of IPP were determined by mass spectrometry( MS) and Fourier transform infrared spectroscopy( FTIR).The change of its space structure after binding Ca^(2+) was studied through FTIR and circular dichroism spectroscopy( CD).The effect of IPP inhibiting calcium phosphate crystal formation was observed by electron microscope. The results showed that phosphate had the priority to binding Ca^(2+) .One mole of IPP could bind four moles of Ca^(2+) and carboxyl group could not bind calcium.Regardless of the presence of Ca^(2+) ,IPP was present in the state of unorded structure in solution under physiological conditions,without any ordered secondary structures.In the supersaturated solution of hydroxylapatite( HAP),IPP could compete with phosphate to bind Ca^(2+) and adsorb to the surfaces of crystal nucleus,which inhibited the nuleation of calcium phosphate and its aggregation to crystal.