The Substrate Capture Mechanism of Mycobacterium tuberculosis Anthranilate Phosphoribosyltransferase Provides a Mode for Inhibition

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• 作者：Alina Castell ; Francesca L. Short ; Genevieve L. Evans ; Tammie V. M. Cookson ; Esther M. M. Bulloch ; Dmitri D. A. Joseph ; Clare E. Lee ; Emily J. Parker ; Edward N. Baker ; J. Shaun Lott
• 刊名：Biochemistry
• 出版年：2013
• 出版时间：March 12, 2013
• 年：2013
• 卷：52
• 期：10
• 页码：1776-1787
• 全文大小：537K
• 年卷期：v.52,no.10(March 12, 2013)
• ISSN：1520-4995

文摘

Anthranilate phosphoribosyltransferase (AnPRT, EC 2.4.2.18) is a homodimeric enzyme that catalyzes the reaction between 5鈥?phosphoribosyl 1鈥?pyrophosphate (PRPP) and anthranilate, as part of the tryptophan biosynthesis pathway. Here we present the results of the first chemical screen for inhibitors against Mycobacterium tuberculosis AnPRT (Mtb-AnPRT), along with crystal structures of Mtb-AnPRT in complex with PRPP and several inhibitors. Previous work revealed that PRPP is bound at the base of a deep cleft in Mtb-AnPRT and predicted two anthranilate binding sites along the tunnel leading to the PRPP binding site. Unexpectedly, the inhibitors presented here almost exclusively bound at the entrance of the tunnel, in the presumed noncatalytic anthranilate binding site, previously hypothesized to have a role in substrate capture. The potencies of the inhibitors were measured, yielding K_i values of 1.5鈥?19 渭M, with the strongest inhibition displayed by a bianthranilate compound that makes hydrogen bond and salt bridge contacts with Mtb-AnPRT via its carboxyl groups. Our results reveal how the substrate capture mechanism of AnPRT can be exploited to inhibit the enzyme鈥檚 activity and provide a scaffold for the design of improved Mtb-AnPRT inhibitors that may ultimately form the basis of new antituberculosis drugs with a novel mode of action.