In silico molecular modelling, structural dynamics simulation and characterization of antifungal nature of β-glucosidase enzyme from Sechium edule

Biochemical and in silico structural properties of a thermo-acid stable β-glucosidase from Beauveria bassiana

β-glucosidase hydrolyses the glycosidic bonds in cellobiose and cello-oligosaccharides, a critical step in the saccharification for biofuel production. Hence, the aim of this study was to gain insights into the biochemical and structural properties of a β-glucosidase from Beauveria bassiana, an entomopathogenic fungus. The β-glucosidase was purified to homogeneity using salt precipitation, ultrafiltration, and chromatographic techniques, attaining a specific activity of 496 U/mg. The molecular mass of the enzyme was then estimated via SDS-PAGE to be 116 kDa, while its activity pattern was confirmed by zymography using 4-methylumbelliferyl-β-d-glucopyranoside. Furthermore, the pH optima and temperature of the enzyme were found to be pH 5.0 and 60 °C respectively; its activity was significantly enhanced by Mg2+ and Na+ and was found to be relatively moderate in the presence of ethanol and dichloromethane. Molecular docking of the modelled B. bassiana β-glucosidase structure with the substrates, viz., 4-nitrophenyl β-d-glucopyranoside and cellobiose, revealed the binding affinity energies of -7.2 and -6.2 (kcal mol-1), respectively. Furthermore, the computational study predicted Lys-657, Asp-658, and Arg-1000 as the core amino acid residues in the catalytic site of the enzyme. This is the first investigation into a purified β-glucosidase from B. bassiana, providing valuable insights into the functional properties of carbohydrases from entomopathogenic fungal endophytes.

Artichoke pectic oligosaccharide characterisation and virtual screening of prebiotic properties using in silico colonic fermentation

The aim of this work was to develop a comprehensive workflow to elucidate molecular features of artichoke pectic oligosaccharides (POS) contributing to high potential prebiotic activity. First, obtainment of artichoke POS by Pectinex® Ultra-Olio was optimised using an artificial neural network. Under optimal conditions (pH 6.86; 1.5 h; enzyme dose 520.5 U/g pectin) POS yield was 624 mg/g pectin. Oligosaccharide structures (M_w < 1.3 kDa) were characterised by MALDI-TOF-MS. Then, conformational analysis of glycosidic bonds was performed by replica exchange molecular dynamics simulations and interaction mechanisms between POS and several microbial glycosidases were proposed by molecular modelling. Chemical information was integrated in virtual simulations of colonic fermentation. Highest hydrolysis rate was obtained for GalA-Rha-GalA trisaccharide, while the presence of partial negative charges and high radius of gyration enhance short chain fatty acid formation in distal colon. Established structure-activity relationships could help the rational design of prebiotics and clinical trials.