三吡啶胺Zn(Ⅱ)配合物作为碳酸酐酶模拟物的研究

A Zinc(II) Complex of Tripyridylamine(TPA) as a Model for Carbonic Anhydrase

利用pH电位滴定法，在25±0.1℃，I＝0.1mol·dm-3KNO3条件下，测定了三吡啶胺（TPA）的质子化常数和三吡啶胺Zn（II）配合物中配位水的解离常数.结果表明，该配合物中与Zn（II）配位的H2O分子的电离常数显著下降，测得pKa为7．8．在25±0．1℃，I＝0．1mol·dm－3NaClO4条件下，pH＝6～9（三羟甲基氨基甲烷缓冲溶液，20mmol·dm-3）范围内，用紫外-可见分光光度法考察了该配合物催化对硝基苯酚乙酸酯（NA）水解的动力学行为，得到了配合物催化酯水解的二级反应速率常数kNP，其最大值为3．32×10－2（mol·dm-3）-1·s－1热力学、动力学的研究结果均说明，三吡啶胺Zn（II）配合物中与Zn（II）配位的OH-是较好的亲核试剂，该配合物是一个较好的碳酸酐水解酶的模拟物．

The protonation constant of TPA and, in its 1:2 (Zn(II):L) complex, thc deprotonation constant of H2O coordinated to Zn(II) have been determined hy pH titration at 25±0.1℃, I=0.1 mol·dm-3 KNO3. They are 4.29 and 7.8, respectively. It is worthy to be noted that the H2O bound to Zn(II) could deprotonate easily near physiology pH.A kinetic study of 4-nitrophenyl acetate(NA) hydrolysis by Zn(II)(TPA)2·H2O complex in 10%(v/v) CH3CN at 25±0.1℃, I=0.1 mol·dm-3 NaClO4, and pH range 6~9(20mmol·dm-3 Tris buffer)，has been carried out. The maximum value of second-order rate constant k((mol·dm-3)-1·s-1) obtained is 3.32×10-2. Thus, Our present model study shows that, like the Zn(II)-enzymes, the Zn(II)-bound OH- in complex can act as a good nucleophile agent to the carbonyl carbons, the Zn(II) complex of TPA is a good model for carbonic anhydrase.