Discovery of Mycobacterium tuberculosis Protein Tyrosine Phosphatase B (PtpB) Inhibitors from Natural Products

Abstract

Protein tyrosine phosphatase B (PtpB) is one of the virulence factors secreted into the host cell by Mycobacterium tuberculosis. PtpB attenuates host immune defenses by interfering with signal transduction pathways in macrophages and, therefore, it is considered a promising target for the development of novel anti-tuberculosis drugs. Here we report the discovery of natural compound inhibitors of PtpB among an in house library of more than 800 natural substances by means of a multidisciplinary approach, mixing in silico screening with enzymatic and kinetics studies and MS assays. Six natural compounds proved to inhibit PtpB at low micromolar concentrations (< 30 µM) with Kuwanol E being the most potent with K i = 1.6 ± 0.1 µM. To the best of our knowledge, Kuwanol E is the most potent natural compound PtpB inhibitor reported so far, as well as it is the first non-peptidic PtpB inhibitor discovered from natural sources. Compounds herein identified may inspire the design of novel specific PtpB inhibitors.

Expression of Mycobacterium tuberculosis Protein Tyrosine Phosphatase B in Escherichia coli and Its Recovery from Inclusion Body

“…Figure 6 shows that PtpB activity is optimum at 37 o C and pH of 6.0. These findings are in agreement to the previous reports (Mascarello et al, 2013;Chiaradia et al, 2008). Thus the recovered PtpB produced by this approach is ready to be utilized in the further study, such as screening of novel inhibitors for PtpB.…”

RETRACTED: Targeting Mycobacterial Enzymes with Natural Products

“…More recently, Zhou et al, (2010) proposed that PtpB promotes mycobacterial survival in cultures of macrophages by inhibiting extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 pathways, and by increasing the phosphorylation of Akt, resulting in reduced production of interleukin-6 and decreased apoptotic activity, respectively. Molecular docking, rescoring, and visual inspection was used by Mascarello et al (2013) to prioritize several natural compounds as possible PtpB inhibitors. Based on the in silico calculations, 14 compounds were selected for biological investigations in vitro.…”

“…Indeed, peptide mass fingerprint analyses performed by mass spectrometry showed that Kuwanol E was able to protect the PtpB catalytic site against the proteolytic activity of trypsin, thus reinforcing the proposed notion that this inhibitor may interact within the PtpB catalytic site. Mascarello et al (2013) opine that the possible binding mode of KuwE with PtpB, investigated by molecular docking, is via hydroxyl groups of KuwE performing H-bond interactions with the catalytic site of PtpB. The MIC value of the investigated compound was, however, not assessed.…”

Yeast as a tool to select inhibitors of the cullin deneddylating enzyme Csn5

“…Selected structures were further filtered with the FILTER application of OpenEye 25 for the presence of the carboxylate moiety and the protonation state of each molecule was assigned by using the FIXPKA application of QUACPAC of OpenEye 26 . Conformational analysis of the database was carried out with the OMEGA software of OpenEye (Santa Fe, NM) 27,28 , by keeping a maximum of 500 conformations for each molecule. Molecular docking was performed by means of the FRED software (Santa Fe, NM) implemented in the OEDocking suite of OpenEye 29 , by saving the best five poses for each molecule and only for the first 50 best scored molecules.…”