Determining the 3-substituted Coumarins inhibitory potential against the HslV protease of E. coli.

OBJECTIVE: The growing bacterial resistance towards classical antibiotics demands the development of novel approaches for the effective treatment of potentially fatal bacterial infections in humans. Proteostasis is crucial for the survival of every living cell, as several important physiological functions depend on well-regulated proteostasis. Within bacteria, the regulation of proteostasis relies on AAA+ (Adenosine 5'-triphosphatases associated with diverse cellular activities), ATPases, such as the HslVU complex (heat shock locus gene products U and V), along with other proteases. The HslVU protease/chaperon complex is thought to be the progenitor of the eukaryotic proteasome that regulates proteostasis mostly in prokaryotes. This study aimed to determine the inhibitory potential of 3-substituted coumarin derivatives against Escherichia coli heat shock locus V (HslV) protease. MATERIALS AND METHODS: In this study, twenty-three derivatives of 3-substituted coumarin were assessed for their inhibitory potential against E. coli HslV protease using both in-vitro and in-silico techniques. RESULTS: Among all the tested compounds, US-I-64, US-I-66, US-I-67, and US-I-68 displayed notable inhibitory potential against the HslV protease, showing IC50 (half maximal inhibitory concentration) values ranging from 0.2 to 0.73 µM. Additionally, the inhibitory potential of these compounds against the eukaryotic proteasome was also evaluated using a separate in-silico study. It was found that these compounds did not bind with the proteasomal active site, suggesting no apparent side effects of these lead molecules. CONCLUSIONS: These identified HslV protease inhibitors can be used for the development of novel and safer anti-bacterial drugs.

Inhibitory potential of triazines and hydrazinyl thiazole substituted chromones against the HslVU protease/chaperone complex, a novel drug target.

OBJECTIVE: Proteostasis is an important process occurring in all living cells and is highly indispensable for cell survival. The HslVU protease/chaperone complex's critical role in regulating proteostasis to maintain a healthy cellular proteome and its presence in pathogenic microbes made it an important drug target. This study aimed to identify small molecular inhibitors of the HslV protease. MATERIALS AND METHODS: Herein, a library of small molecules belonging to the triazine and chromone families has been evaluated for their inhibitory potential against the E. coli HslV protease using both in silico and in vitro techniques. RESULTS: Four compounds, i.e., SHS-II-123a, SHS-II-147a, US-IV-89, and US-IV-92, were identified as potential inhibitors of the HslV protease having IC50 values in the range of 0.1 to 0.32 µM. Additionally, these compounds' drug-likeness and ADMET profiles indicated their compatibility to be considered safer drug candidates. CONCLUSIONS: To the best of our knowledge, this is the first report on small molecules having inhibitory effects on the HslVU complex. These identified compounds can be efficiently subjected to further investigations to develop novel and safer antimicrobial agents.

Author Correction: Inhibitory potential of triazines and hydrazinyl thiazole substituted chromones against the HslVU protease/chaperone complex, a novel drug target.

Correction to: European Review for Medical and Pharmacological Sciences 2022; 26 (22): 8567-8575. DOI: 10.26355/eurrev_202211_30392-PMID: 36459037-published online on November 30, 2022. After publication, the authors applied some corrections to the text: - Dr. U. Salar's affiliation has been corrected as follows: Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, Pakistan. - The values in the row "Binding energy with HsIV (Kcal/mol)" Table I have been corrected as follows: from -8.4 into -9.0; from -8.6 into -9.2; from -8.0 into -8.5 from -8.3 into -8.7. There are amendments to this paper. The Publisher apologizes for any inconvenience this may cause. https://www.europeanreview.org/article/30392.

Natural honey modulates physiological glycemic response compared to simulated honey and D-glucose.

The present study is undertaken to find out the relative glycemic tolerance of natural honey compared with simulated honey and D-glucose using oral glucose tolerance tested up to 180 min. Twenty-six healthy human subjects with mean age of 28.6 +/- 9.3 y were randomly divided into 3 groups, that is, natural honey consumers (NHC; n= 13), simulated honey consumers (AHC; n= 6), and D-glucose consumers (DGC; n= 7). After recording fasting blood glucose, the participants consumed either natural honey or simulated honey or D-glucose (1g/kg body weight). Subsequently, additional plasma glucose levels (PGLs) were recorded at 60, 120, and 180 min. At 60 min, DGC and AHC group members exhibited similar PGL elevation (that is, 52% and 47%, respectively) compared to NHC group with only 20% increment. On the other hand, after 180 min, 20% decrease in PGL was observed in the DGC group compared to 9.75% reduction in the NHC group. These observations are primarily in line with earlier studies. Results analyzed by one-way analysis of variance (ANOVA) showed significant differences between all 3 tested groups with F-statistic (19.96) and P value (< 0.005). Coefficient of variation of the NHC, AHC, and DGC groups were 14.8%, 20.2%, and 27.5%, respectively. Posthoc tests showed that glucose response was significantly lower in the NHC group at all time points (P < 0.005) compared to the AHC and DGC groups. In conclusion, natural honey stabilizes physiological glycemic response with rebound recovery of PGL.

Homology modeling of nematode Caenorhabditis elegans CED3 protein-inhibitor complex.

CED3 protein, the product of a gene necessary for programmed cell death in the nematode Caenorhabditis elegans, is related to a highly specific cysteine protease family i.e., caspases. A tertiary-structural model has been constructed of a complex of the CED3 protein with tetrapeptide-aldehyde inhibitor, Ac-DEVD-CHO. The conformation of CED3 protein active site and the general binding features of inhibitor residues are similar to those observed in other caspases. The loop segment (Phe380-Pro387) binds with the P4 Asp in a different fashion compared to caspase-3. The comparative modeling of active sites from caspase-3 and CED3 protein indicated that although these enzymes require Asp at the position P4, variation could occur in the binding of this residue at the S4 subsite. This model allowed the definition of substrate specificity of CED3 protein from the structural standpoint and provided insight in designing of mutants for structure-function studies of this classical caspase homologue.

Predicted three-dimensional structural models of venom serine protease inhibitors and their interactions with trypsin and chymotrypsin.

Three homology models of trypsin and chymotrypsin inhibitor polypeptides from snake venom of Naja naja naja and Leaf-nosed viper in the unbound state and in complex with trypsin and chymotrypsin were built based on homology to bovine pancreatic trypsin inhibitor (BPTI). These venom inhibitors belong to the Kunitz-type inhibitor family, which is characterized by a distinct tertiary fold with three-conserved disulfide bonds. The general folding pattern in these trypsin and chymotrypsin inhibitor homology models is conserved when compared to BPTI. The respective orientations of the inhibitors bound to trypsin/chymotrypsin are similar to that of BPTI bound to bovine trypsin/chymotrypsin. The principal binding loop structure of the inhibitors fills the active site of enzymes in a substrate-like conformation and forms a series of independent main-chain and side-chain interactions with enzymes. In order to provide the possible fingerprints for molecular recognition at the enzyme-inhibitor interface, a detailed theoretical analysis of the interactions between the principal binding loop of these inhibitors and active site of trypsin/chymotrypsin is performed based on available crystal structural, site-directed mutagenetic, kinetic, and sequence analysis studies. Despite the variations present at different positions of the principal binding loop of trypsin and chymotrypsin inhibitor models from Leaf-nosed viper and cobra Naja naja naja, respectively (designated as LnvTI and NCI), there are favorable subsite binding interactions which are expected to exhibit equally potent inhibitory activity as BPTI. On the contrary, significant mutations at several secondary specificity positions in the Naja naja naja trypsin inhibitor (designated as NTI) are likely to affect different inhibitor-enzyme-subsites interactions. This may explain the observed increased inhibitory activity of this polypeptide on a structural basis.

Molecular modeling of human procathepsin E: analysis of salt-bridge interactions between propeptide and enzyme segment.

A three-dimensional structural model of human cathepsin E zymogen (e. g., procathepsin E) has been constructed based upon the crystal structures of porcine pepsinogen. The overall protein folding features of the model are similar to those observed in the template structures. The propeptide packs into the active-site cleft with a similar secondary structural pattern and is associated with enzyme segment by salt-bridges, hydrogen bondings, and hydrophobic interactions. As judged from the model, the salt bridges present between the propeptide and enzyme segment show remarkable variations compared to porcine pepsinogen and human progastricin structures. Mapping of these interactions revealed that human procathepsin E might engage a different structural motif (alpha-helix;12P-19P) for protecting/blocking of catalytic site compared to pepsinogen and progastricin.