New classes of alanine racemase inhibitors identified by high-throughput screening show antimicrobial activity against Mycobacterium tuberculosis.

Abstract

BACKGROUND:

In an effort to discover new drugs to treat tuberculosis (TB) we chose alanine racemase as the target of our drug discovery efforts. In Mycobacterium tuberculosis, the causative agent of TB, alanine racemase plays an essential role in cell wall synthesis as it racemizes L-alanine into D-alanine, a key building block in the biosynthesis of peptidoglycan. Good antimicrobial effects have been achieved by inhibition of this enzyme with suicide substrates, but the clinical utility of this class of inhibitors is limited due to their lack of target specificity and toxicity. Therefore, inhibitors that are not substrate analogs and that act through different mechanisms of enzyme inhibition are necessary for therapeutic development for this drug target.

METHODOLOGY/PRINCIPAL FINDINGS:

To obtain non-substrate alanine racemase inhibitors, we developed a high-throughput screening platform and screened 53,000 small molecule compounds for enzyme-specific inhibitors. We examined the 'hits' for structural novelty, antimicrobial activity against M. tuberculosis, general cellular cytotoxicity, and mechanism of enzyme inhibition. We identified seventeen novel non-substrate alanine racemase inhibitors that are structurally different than any currently known enzyme inhibitors. Seven of these are active against M. tuberculosis and minimally cytotoxic against mammalian cells.

CONCLUSIONS/SIGNIFICANCE:

This study highlights the feasibility of obtaining novel alanine racemase inhibitor lead compounds by high-throughput screening for development of new anti-TB agents.

• Authors: Karen G Anthony, Ulrich Strych, Kacheong R Yeung, Carolyn S Shoen, Oriana Perez, Kurt L Krause, Michael H Cynamon, Paul A Aristoff, Raymond A Koski
• Journal: PloS one (PLoS One) Vol. 6 Issue 5 Pg. e20374 ( 2011) ISSN: 1932-6203 [Electronic] United States
• PMID: 21637807 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Anti-Infective Agents
• Enzyme Inhibitors
• Alanine Dehydrogenase
• Alanine Racemase

Topics

• Alanine Dehydrogenase (metabolism)
• Alanine Racemase (antagonists & inhibitors, chemistry, metabolism, pharmacology)
• Anti-Infective Agents (analysis, chemistry, classification, pharmacology)
• Cell Death (drug effects)
• Enzyme Inhibitors (analysis, chemistry, classification, pharmacology)
• HeLa Cells
• High-Throughput Screening Assays (methods)
• Humans
• Inhibitory Concentration 50
• Kinetics
• Mass Spectrometry
• Microbial Sensitivity Tests
• Mycobacterium tuberculosis (drug effects)
• Substrate Specificity (drug effects)