Rapid Phosphodiester Hydrolysis by an Ammonium-Functionalized Copper(II) Complex. A Model for the Cooperativity of Metal Ions and NH-Acidic Groups in Phosphoryl Transfer Enzymes
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- 作者：Endre Kö ; vá ; ri and Roland Krä ; mer
- 刊名：Journal of the American Chemical Society
- 出版年：1996
- 出版时间：December 18, 1996
- 年：1996
- 卷：118
- 期：50
- 页码：12704 - 12709
- 全文大小：243K
- 年卷期：v.118,no.50(December 18, 1996)
- ISSN：1520-5126
文摘
The copper(II) complexes[(Ln)Cu(NO3)4·2(H2O)](n = 1: 1, n = 2:2) of the ammonium-functionalizedligands[6,6'-(Me2HNCH2C
images/entities/tbd1.gif">C)2bpy]2+(L1) and[6,6'-(Me3NCH2Cimages/entities/tbd1.gif">C)2bpy]2+(L2) were prepared. Hydrolysisofthe activated phosphodiester bis(p-nitrophenyl)phosphate (BNPP) by these complexes in ethanol-water 19:1 at20images/entities/deg.gif">C was investigated. The rate constants for cleavage of thebound phosphodiester at pH 6.6 are kcat =4.4(±0.4) ×10-3 s-1 for(L1)Cu andkcat = 4(±1) ×10-6 s-1 for(L2)Cu.(L1)Cu accelerateshydrolysis of BNPP 4 × 107-foldand is 1000 times more reactive than(L2)Cu. This suggests thatthe high reactivity of (L1)Cu isrelated to theinteraction of the acidic -NMe2H+ groupwith the phosphodiester substrate. Bifunctional binding of aphosphateester by metal coordination and hydrogen bonding with one ammoniumgroup is observed in the crystallographicallycharacterized complex[(L1)2Cu2(1,3-images/entities/mgr.gif">-O3POPh)2(OH2)2](NO3)4(3). A plausible mechanism of BNPP cleavageby(L1)Cu includes metal-hydroxideattack to the phosphodiester which is doubly activated by coordinativeand hydrogenbonding. The copper(II) complex ofL1 represents a simple model for theefficient cooperativity of metal ions andNH-acidic amino acid side chains (Lys-ammonium, Arg-guanidinium,His-imidazolium) in enzymes that catalyzethe cleavage of phosphate di- and monoesters.