Experimental and theoretical spectroscopic (FT-IR, FT-Raman, UV-VIS) analysis, natural bonding orbitals and molecular docking studies on 2-bromo-6-methoxynaphthalene: A potential anti-cancer drug

Optimization of subtilisin production from Bacillus subtilis strain ZK3 and biological and molecular characterization of synthesized subtilisin capped nanoparticles

The increase and dissemination of multi-drug resistant bacteria have presented a major healthcare challenge, making bacterial infections a significant concern. The present research contributes towards the production of bioactive subtilisin from a marine soil isolate Bacillus subtilis strain ZK3. Custard apple seed powder (raw carbon) and mustard oil cake (raw nitrogen) sources showed a pronounced effect on subtilisin production. A 7.67-fold enhancement in the production was evidenced after optimization with central composite design-response surface methodology. Subtilisin capped silver (AgNP) and zinc oxide (ZnONP) nanoparticles were synthesized and characterized by UV-Visible spectroscopy. Subtilisin and its respective nanoparticles revealed significant biological properties such as, antibacterial activity against all tested pathogenic strains with potential against Escherichia coli and Pseudomonas aeruginosa. Prospective antioxidant behavior of subtilisin, AgNP and ZnONP was evidenced through radical scavenging assays with ABTS and DPPH. Subtilisin, AgNP and ZnONP revealed cytotoxic effect against cancerous breast cell lines MCF-7 with IC50of 83.48, 3.62 and 7.57 µg/mL respectively. Characterizations of nanoparticles were carried out by Fourier transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-ray, X-ray diffraction, thermogravimetric analysis and atomic force microscopy analysis to elucidate the structure, surface and thermostability properties. The study proposes the potential therapeutic applications of subtilisin and its nanoparticles, a way forward for further exploration in the field of healthcare.

Gene expression and molecular characterization of recombinant subtilisin from Bacillus subtilis with antibacterial, antioxidant and anticancer properties

This study investigated the multifunctional attributes such as, antibacterial, antioxidant and anticancer potential of recombinant subtilisin. A codon-optimized subtilisin gene was synthesized from Bacillus subtilis and was successfully transformed into E. coli DH5α cells which was further induced for high level expression in E. coli BL21 (DE3). An affinity purified ~40 kDa recombinant subtilisin was obtained that revealed to be highly alkali-thermostable based on the thermodynamic parameters. The kinetic parameters were deduced that indicated higher affinity of N-Suc-F-A-A-F-pNA substrate towards subtilisin. Recombinant subtilisin demonstrated strong antibacterial activity against several pathogens and showed minimum inhibitory concentration of 0.06 μg/mL against B. licheniformis and also revealed high stability under the influence of several biochemical factors. It also displayed antioxidant potential in a dose dependent manner and exhibited cell cytotoxicity against A549 and MCF-7 cancerous cell lines with IC50 of 5 μM and 12 μM respectively. The identity of recombinant subtilisin was established by MALDI-TOF mass spectrum depicting desired mass peaks and N-terminal sequence as MRSK by MALDI-TOF-MS. The deduced N- terminal amino acid sequence by Edman degradation revealed high sequence similarity with subtilisins from Bacillus strains. The structural and functional analysis of recombinant antibacterial subtilisin was elucidated by Raman, circular dichroism and nuclear magnetic resonance spectroscopy and thermogravimetric analysis. The results contribute to the development of highly efficient subtilisin with enhanced catalytic properties making it a promising candidate for therapeutic applications in healthcare industries.

Pentafuhalol-B, a Phlorotannin from Brown Algae, Strongly Inhibits the PLK-1 Overexpression in Cancer Cells as Revealed by Computational Analysis

Polo-like kinase-1 (PLK-1) is an essential mitotic serine/threonine (Ser/Thr) kinase that belongs to the Polo-like kinase (PLK) family and is overexpressed in non-small cell lung cancer (NSCLC) via promotion of cell division. Therefore, PLK-1 may act as a promising target for the therapeutic cure of various cancers. Although a variety of anti-cancer drugs, both synthetic and naturally occurring, such as volasertib, onvansertib, thymoquinone, and quercetin, are available either alone or in combination with other therapies, they have limited efficacy, especially in the advanced stages of cancer. To the best of our knowledge, no anticancer agent has been reported from marine algae or microorganisms to date. Thus, the aim of the present study is a high-throughput virtual screening of phlorotannins, obtained from edible brown algae, using molecular docking and molecular dynamic simulation analysis. Among these, Pentafuhalol-B (PtB) showed the lowest binding energy (best of triplicate runs) against the target protein PLK-1 as compared to the reference drug volasertib. Further, in MD simulation (best of triplicate runs), the PtB-PLK-1 complex displayed stability in an implicit water system through the formation of strong molecular interactions. Additionally, MMGBSA calculation (best of triplicate runs) was also performed to validate the PtB-PLK-1 complex binding affinities and stability. Moreover, the chemical reactivity of PtB towards the PLK-1 target was also optimised using density functional theory (DFT) calculations, which exhibited a lower HOMO-LUMO energy gap. Overall, these studies suggest that PtB binds strongly within the pocket sites of PLK-1 through the formation of a stable complex, and also shows higher chemical reactivity than the reference drug volasertib. The present study demonstrated the inhibitory nature of PtB against the PLK-1 protein, establishing its potential usefulness as a small molecule inhibitor for the treatment of different types of cancer.