7m7v
Crystal Structure of Mtb Pks13 Thioesterase domain in complex with Compound 6
Structural highlights
FunctionPKS13_MYCTU Involved in the biosynthesis of mycolic acids (PubMed:19436070, PubMed:23770708, PubMed:25467124). Forms, with FadD32, the initiation module of the mycolic condensation system (PubMed:19436070, PubMed:19477415, PubMed:25467124). Synthesizes, in coupled reaction with FadD32, the biosynthetic precursors of mycolic acids, alpha-alkyl beta-ketoacids, via the condensation of two long chain fatty acid derivatives, a very long meromycoloyl-AMP and a shorter 2-carboxyacyl-CoA (PubMed:19436070, PubMed:25467124). The acyl chain of the acyl-AMP produced by FadD32 is specifically transferred onto the N-terminal ACP domain of Pks13, and then transferred onto the KS domain. The extender unit carboxyacyl-CoA is specifically loaded onto the AT domain, which catalyzes the covalent attachment of the carboxyacyl chain to its active site, and its subsequent transfer onto the P-pant arm of the C-terminal ACP domain. The KS domain catalyzes the condensation between the two loaded fatty acyl chains to produce an alpha-alkyl beta-ketothioester linked to the C-ACP domain (PubMed:19436070). Then, the thioesterase-like domain acts as a transacylase and is responsible for both the release and the transfer of the alpha-alkyl beta-ketoacyl chain onto a polyol acceptor molecule, particularly trehalose, leading to the formation of the trehalose monomycolate precursor (PubMed:25467124).[1] [2] [3] [4] Publication Abstract from PubMedWith increasing drug resistance in tuberculosis (TB) patient populations, there is an urgent need for new drugs. Ideally, new agents should work through novel targets so that they are unencumbered by preexisting clinical resistance to current treatments. Benzofuran 1 was identified as a potential lead for TB inhibiting a novel target, the thioesterase domain of Pks13. Although, having promising activity against Mycobacterium tuberculosis, its main liability was inhibition of the hERG cardiac ion channel. This article describes the optimization of the series toward a preclinical candidate. Despite improvements in the hERG liability in vitro, when new compounds were assessed in ex vivo cardiotoxicity models, they still induced cardiac irregularities. Further series development was stopped because of concerns around an insufficient safety window. However, the demonstration of in vivo activity for multiple series members further validates Pks13 as an attractive novel target for antitubercular drugs and supports development of alternative chemotypes. Optimization of TAM16, a Benzofuran That Inhibits the Thioesterase Activity of Pks13; Evaluation toward a Preclinical Candidate for a Novel Antituberculosis Clinical Target.,Wilson C, Ray P, Zuccotto F, Hernandez J, Aggarwal A, Mackenzie C, Caldwell N, Taylor M, Huggett M, Mathieson M, Murugesan D, Smith A, Davis S, Cocco M, Parai MK, Acharya A, Tamaki F, Scullion P, Epemolu O, Riley J, Stojanovski L, Lopez-Roman EM, Torres-Gomez PA, Toledo AM, Guijarro-Lopez L, Camino I, Engelhart CA, Schnappinger D, Massoudi LM, Lenaerts A, Robertson GT, Walpole C, Matthews D, Floyd D, Sacchettini JC, Read KD, Encinas L, Bates RH, Green SR, Wyatt PG J Med Chem. 2022 Jan 13;65(1):409-423. doi: 10.1021/acs.jmedchem.1c01586. Epub, 2021 Dec 15. PMID:34910486[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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