Structural Analysis of Free N-Glycans in α-Glucosidase Mutants of Saccharomyces cerevisiae: Lack of the Evidence for the Occurrence of Catabolic α-Glucosidase Acting on the N-Glycans

Antioxidant activity and α-glucosidase inhibitability of Distichochlamys citrea M.F. Newman rhizome fractionated extracts: in vitro and in silico screenings

Distichochlamys citrea M.F. Newman (commonly known as “Black Ginger”) is an endemic plant to Vietnam and has been extensively exploited by folk medication for treatments of infection-related diseases and diabetes. In this work, its rhizomes were subjected to fractionated extraction, phytochemical examination, evaluation of antioxidant effect by DDPH free radical neutralization, and inhibitory activity toward α-glucosidase. The compositional components were subjected to in silico screening, including density functional theory calculation, molecular docking simulation, physicochemical analysis, and pharmacokinetic regression. In the trials, EtOAc fraction is found as the bioactive part of most effectiveness, regarding both antioxidant effect (IC₅₀ = 90.27 µg mL⁻¹) and α-glucosidase inhibitory activity (IC₅₀ = 115.75 μg mL⁻¹). Chemical determination reveals there are 13 components of its composition. DFT-based calculations find no abnormal constraints in their structures. Docking-based simulation provides order of inhibitory effectiveness: 3-P53341 > 12-P53341 > 7-P53341 > 4-P53341 > 11-P53341 > 10-P53341. QSARIS-based investigations implicate their biocompatibility. ADMET-based regressions indicate that all candidates are generally safe for medicinal applications. The findings would contribute to the basis for further studies on the chemical compositions of Distichochlamys citrea and their biological activities.

Abrogation of glucosidase I-mediated glycoprotein deglucosylation results in a sick phenotype in fission yeasts: Model for the human MOGS-CDG disorder

Glucosidase I (GI) removes the outermost glucose from protein-linked Glc₃Man₉GlcNAc₂ (G3M9) in the endoplasmic reticulum (ER). Individuals with congenital disorders of glycosylation MOGS-CDG bear mutations in the GI-encoding gene (gls1). Although GI absence has been reported to produce lethality in Schizosaccharomyces pombe yeasts, here we obtained two viable Δgls1 mutants, one with a very sick but not lethal phenotype (Δgls1-S) and the other with a healthier one (Δgls1-H). The sick strain displayed only G3M9 as an ER protein-linked oligosaccharide, whereas the healthier strain had both G3M9 and Man₉GlcNAc₂ The lipid-linked oligosaccharide patterns of the two strains revealed that the most abundantly formed glycans were G3M9 in Δgls1-S and Glc₂Man₉GlcNAc₂ in Δgls1-H, suggesting reduced Alg10p glucosyltransferase activity in the Δgls1-H strain. A mutation in the alg10 ⁺ gene was indeed observed in this strain. Our results indicated that abrogated G3M9 deglucosylation was responsible for the severe defects observed in Δgls1-S cells. Further studies disclosed that the defects could not be ascribed to disruption of glycoprotein entrance into calnexin-folding cycles, inhibition of the oligosaccharyltransferase by transfer reaction products, or reduced proteasomal degradation of misfolded glycoproteins. Lack of triglucosylated glycoprotein deglucosylation neither significantly prevented glycan elongation in the Golgi nor modified the overall cell wall monosaccharide composition. Nevertheless, it resulted in a distorted cell wall and in the absence of underlying ER membranes. Furthermore, Golgi expression of human endomannosidase partially restored normal growth in Δgls1-S cells. We propose that accumulation of G3M9-bearing glycoproteins is toxic and at least partially responsible for defects observed in MOGS-CDG.

Starch biotransformation into isomaltooligosaccharides using thermostable alpha-glucosidase from Geobacillus stearothermophilus

The present study first identified the biotransformation of starch as a novel preparation method was investigated using the alpha-transglucosidase-producing Geobacillus stearothermophilus U2. Subsequently, 5 L- and 20 L-scale fermentations were performed. After isolation and purification, liquid alpha-glucosidase preparations were obtained. Through covalent cross-linking and adsorption cross-linking using chitosan as the carrier and glutaraldehyde as the crosslinking agent, the conditions for immobilization of alpha-glucosidase on chitosan were determined. Moreover, Isomaltooligosaccharides (IMOs) were then prepared using chitosan membrane-immobilized alpha-glucosidase, beta-amylase, pullulanase, fungal alpha-amylase and starch as substrate. The mixed syrup that contained IMOs was evaluated and analyzed by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). In addition, small-scale preparation of IMOs was performed. These results are a strong indication that the alpha-transglucosidase-producing G. stearothermophilus as a potential application technique can be successfully used to prepare industrial IMOs.