This class of chemical compounds attacks TB by inhibiting methionine aminopeptidase (MetAP), an essential enzyme found in organisms ranging from bacteria to humans, and that clearly has been conserved throughout evolution because of its important task of ensuring the proper manufacture of proteins.
"The MetAP inhibitors we discovered are hits, or leads in the sense that they provide a framework — a starting point — for the future development of an anti-TB drug," says Jun O. Liu, Ph.D., professor of pharmacology and molecular sciences, Johns Hopkins University School of Medicine.The research appears in the January 29 edition of Chemistry & Biology.
"If you knock out this enzyme in TB bacteria, the bacteria will not survive," Liu says. "We expected that would happen, and confirmed it by manipulating how much enzyme is expressed to see what happens to the sensitivity of the bacteria when inhibitors are present."
What caught the team by surprise, however, was finding a potent class of compounds (called 2,3-dichloro-1, 4-naphthoquinone) that inhibits this enzyme. That discovery involved the use of large-scale, high-throughput screening of 175,000 compounds and measuring the potencies of a dozen related hits against the enzyme.
The final experiment by the team was to test the MetAP inhibitors on TB bacteria in culture to see if it had any effect on bacteria growth.
"Judging from potency, a MetAP inhibibitor alone probably won't wipe out TB," Liu says. "TB is so hard to treat that the standard therapy involves a cocktail of multiple drugs; no single compound is powerful enough. Our hope is that someday an inhibitor of MetAP will become a new component to enhance the existing therapy."
This study was funded by the National Institutes of Health.
In addition to Liu, authors of this paper are Omonike Olaleye, Tirumalai R. Raghunand, Shridhar Bhat, Sandeep Tyagi, Gyanu Lamichhane, Peihua Gu, Jiangbing Zhou, Ying Zhang, Jacques Grosset, and William R. Bishai, all of Johns Hopkins.
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