水杨醛缩芳胺席夫碱铜(Ⅱ)配合物抑制蛋白酪氨酸磷酸酶活性研究

Evaluation of Cu(Ⅱ) Complexes with Schiff Base of Salicylanilide as the Inhibitors of Protein Tyrosine Phosphatases

为了探讨席夫碱配体上取代基变化对其配合物抑制蛋白酪氨酸磷酸酶(PTPs)活性的影响,合成表征了水杨醛缩芳胺席夫碱铜髤配合物[Cu(X-pimp)2](X=Cl,Br和Acetyl),用紫外光谱滴定和pH电位滴定研究了[Cu(Cl-pimp)2]的溶液结构,并测定了3个配合物抑制4种PTPs活性的IC50值。结果表明它们都能够有效抑制PTP1B和TCPTP(0.20μmol·L-1<IC50<0.31μmol·L-1),但对SHP-1的抑制较弱且对SHP-2几乎无抑制作用。分析并与文献结果比较发现,席夫碱配体上苯胺对位取代基类型的改变不会显著影响其抑制作用,但取代基位置的改变可能会影响其选择性。稳态动力学研究表明[Cu(Cl-pimp)2]能够非竞争性抑制PTP1B活性,而荧光光谱实验表明二者形成了键合常数为9.3×106 L·mol-1的1∶1复合物。我们推测,配合物可能结合在PTP1B非活性区域,间接导致活性中心结构变化,从而抑制其活性。

To improve the inhibitory selectivity and explore the substitution effect of the Schiff base ligands on the inhibitory effect of the complex against the PTPs, three Cu（Ⅱ） complexes, [Cu（X-pimp）2]（X-pimp =2-（（4-Xphenylimino）methyl） phenol）, X=Cl, Br, and Acetyl）, were prepared and characterized by X-ray, EA, IR, UV-Vis and ESI-MS. Taking [Cu（Cl-pimp）2] complex as an example, the solution species distribution with different p H values and the main existing form under the p H neutral condition were investigated using both the p H potentiometric and UV titrations, indicating that the ration of Cl-pimp ligand and Cu（Ⅱ） ion in the complex was 2：1 in an aqueous solution and [Cu（Cl-pimp）2H-1]-is the main existing form in the p H neutral condition. Then the inhibitory activities of these complexes against above-mentioned protein tyrosine phosphatase 1B（PTP1B）, T-cell protein tyrosine phosphatase（TCPTP）, Src homology phosphatase 1（SHP-1）, and Src homology phosphates 2（SHP-2）was evaluated using IC50 values. The results revealed that these three complexes showed similar inhibitory behaviours, i.e. potent effect against PTP1 B and TCPTP（0.20 μmol·L^-1IC500.31 μmol·L^-1）, the relatively lower effect against SHP-1（2.7 μmol·L^-1IC504.7 μmol·L^-1）, while negligible effect against SHP-2（IC50100 μmol·L^-1）,which indicated that the type of substituents on the papa position of phenylimino of the Schiff base ligand did not influence the inhibitory effect of the complexes against PTPs obviously. However, comparing the current results to that of the above-mentioned previous work, we can find that the change in the position of the substituents may change the selectivity of inhibitory effect of the complexes against PTPs. The interactions between the complexes and PTPs were studied using [Cu（Cl-pimp）2] and PTP1 B as the representatives. The kinetics assays showed that the complex inhibited PTP1 B in a non-competitive mode and the inhibition constant was calculated to be 0.35 μmol·L^-1. The fluorescence titration revealed that the complex bound to PTP1 B with the molar ration of 1 ∶1 and the binding constant of 9.3×106L·mol^-1. We infer that the [Cu（Cl-pimp）2] complex may bind firmly to inactive area of PTP1 B and indirectly lead to the structural changes to the active center, which inhibits the activity of PTP1B.