Discovery of AMP Mimetics that Exhibit High Inhibitory Potency and Specificity for AMP Deaminase
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- 作者：Mark D. Erion ; Srinivas Rao Kasibhatla ; Brett C. Bookser ; Paul D. van Poelje ; M. Rami Reddy ; Harry E. Gruber ; and James R. Appleman
- 刊名：Journal of the American Chemical Society
- 出版年：1999
- 出版时间：January 20, 1999
- 年：1999
- 卷：121
- 期：2
- 页码：308 - 319
- 全文大小：261K
- 年卷期：v.121,no.2(January 20, 1999)
- ISSN：1520-5126
文摘
The first potent, specific, and cell-penetrable AMP deaminase (AMPDA) inhibitors were discoveredthrough an investigation of 3-substituted 3,6,7,8-tetrahydroimidazo[4,5-d][1,3]diazepin-8-ol analogues. Inhibitionconstants for the most potent inhibitors were 105-fold lower than the KM for the substrate AMP. High affinityrequired the presence of both the 8-hydroxyl and the 3-substituent and is postulated to arise from a cooperativeinteraction that reduces binding entropy costs and enables the diazepine base to adopt a binding conformationthat mimics the transition-state (TS) structure. The high specificity of the inhibitor series for AMPDA relativeto other AMP-binding enzymes (>105) is attributed in part to the diazepine base which favors interactionswith residues used to stabilize the TS structure and precludes interactions typically used by AMP-bindingenzymes to bind AMP. In contrast, discrimination between AMPDA and adenosine deaminase (ADA), twoenzymes postulated to stabilize a similar TS structure, is highly dependent on the 3-substituent. Replacementof the ribose group in the potent ADA inhibitor coformycin (Ki (ADA) = 10-11 M vs Ki (AMPDA) = 3 ×10-6 M) with 3-carboxy-4-bromo-5,6,7,8-tetrahydronaphthylethyl led to a >1010-fold change in specificity(Ki (ADA) > 10-3 M vs Ki (AMPDA) = 2 × 10-9 M). Inhibitors from the series readily penetrate cells andinhibit intracellular AMPDA activity. Incubation of isolated rat hepatocytes with AMPDA inhibitors had noeffect on secondary metabolite levels during normoxic conditions but led to increased adenosine productionand adenylate sparing under conditions that induce net ATP breakdown. These results suggest that inhibitorsof AMPDA may represent site- and event-specific drugs that could prevent or attenuate ischemic tissue damageresulting from a stroke or a heart attack.