Inhibition of the Escherichia coli 6-Oxopurine Phosphoribosyltransferases by Nucleoside Phosphonates: Potential for New Antibacterial Agents

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• 作者：Dianne T. Keough ; Dana Hockov谩 ; Dominik Rejman ; Petr 艩pa膷ek ; Silvie Vrbkov谩 ; Marcela Kre膷merov谩 ; Wai Soon Eng ; Harmen Jans ; Nicholas P. West ; Lieve M. J. Naesens ; John de Jersey ; Luke W. Guddat
• 刊名：Journal of Medicinal Chemistry
• 出版年：2013
• 出版时间：September 12, 2013
• 年：2013
• 卷：56
• 期：17
• 页码：6967-6984
• 全文大小：818K
• 年卷期：v.56,no.17(September 12, 2013)
• ISSN：1520-4804

文摘

Escherichia coli (Ec) cells possess two purine salvage enzymes: xanthine-guanine phosphoribosyltransferase (XGPRT) and hypoxanthine phosphoribosyltransferase (HPRT). EcXGPRT shares a common structural feature with other members of this family, a flexible loop that closes over the active site during catalysis. The replacement of six of these amino acids by alanine has no effect on the K_m for the two substrates. However, the K_i for the nucleoside monophosphate increases by 27-fold, and the k_cat is reduced by 200-fold. Nucleoside phosphonates (NP) are good inhibitors of EcXGPRT and EcHPRT, with K_i values as low as 10 nM. In the absence of the flexible loop, these values increase by 5- to 30-fold, indicating the importance of the loop for high-affinity inhibition. Crystal structures of two NPs in complex with EcXGPRT explain the tight binding. Prodrugs of NPs with low K_i values for EcXGPRT or EcHPRT exhibit IC₅₀ values between 5 and 23 渭M against Mycobacterium tuberculosis in cell-based assays, suggesting that these compounds are therapeutic leads against pathogenic bacteria.