Structure and Function Insight of the α-Glucosidase QsGH13 From Qipengyuania seohaensis sp. SW-135

In Vitro Biological Evaluation and In Silico Studies of a New Anthraquinone From Zingiber Cassumunar Roxb. in Type 2 Diabetes Management

A novel diphenyl-anthraquinone compound, cassuquinone A (CA), was isolated from the rhizomes of Zingiber cassumunar. Structural elucidation was accomplished using detailed nuclear magnetic resonance and high-resolution mass spectroscopy-electrospray ionization techniques, revealing a symmetrical anthraquinone core with methoxylated aromatic rings. CA exhibited potent α-glucosidase (AR) inhibitory activity with an IC₅₀ of 11.72 µM, significantly more potent than the positive control, acarbose (IC₅₀ = 190.60 µM), highlighting its potential as an antidiabetic agent. Molecular docking studies indicated stable binding of CA to AR, with key interactions involving Arg315, Phe314, Glu411, Val232, and Ser240, contributing to its high docking score. Additionally, molecular dynamics simulations demonstrated that CA stabilizes the AR structure by reducing the enzyme's flexibility, especially within the active site, which may hinder substrate access and product release.

Structural and functional comparisons of salivary α-glucosidases from the mosquito vectors Aedes aegypti, Anopheles gambiae, and Culex quinquefasciatus

Mosquito vectors of medical importance both blood and sugar feed, and their saliva contains bioactive molecules that aid in both processes. Although it has been shown that the salivary glands of several mosquito species exhibit α-glucosidase activities, the specific enzymes responsible for sugar digestion remain understudied. We therefore expressed and purified three recombinant salivary α-glucosidases from the mosquito vectors Aedes aegypti, Anopheles gambiae, and Culex quinquefasciatus and compared their functions and structures. We found that all three enzymes were expressed in the salivary glands of their respective vectors and were secreted into the saliva. The proteins, as well as mosquito salivary gland extracts, exhibited α-glucosidase activity, and the recombinant enzymes displayed preference for sucrose compared to p-nitrophenyl-α-D-glucopyranoside. Finally, we solved the crystal structure of the Ae. aegypti α-glucosidase bound to two calcium ions at a 2.3 Ångstrom resolution. Molecular docking suggested that the Ae. aegypti α-glucosidase preferred di- or polysaccharides compared to monosaccharides, consistent with enzymatic activity assays. Comparing structural models between the three species revealed a high degree of similarity, suggesting similar functional properties. We conclude that the α-glucosidases studied herein are important enzymes for sugar digestion in three mosquito species.

Metabolomics-based pharmaceutical evaluation of different parts of Swertia chirayita (Roxb.) Buch.-Ham. ex C.B. Clarke from the western Himalayas

Swertia species are common ingredients in numerous herbal remedies. It is also used to treat a wide range of illnesses and possess diverse therapeutic activities. The aim of the study is to elucidate the comprehensive metabolomics profile of Swertia chirayita and the role of various extraction methods in the phytochemical compositions of the extracts of S. chirayita, and their antioxidant and enzyme inhibitory activities. Extraction of the stems, leaves, and flowering tops of S. chirayita was performed by maceration, infusion, and soxhlation using methanol and water as solvent. Extracts were subjected to phytochemical profiling by a liquid-chromatographic system. Antioxidant and enzyme inhibitory activity was carried out. The metabolomics profiling showed that a diverse range of specialized metabolites were present in the stems and leaves & flowering tops of the plant. All the extracts showed substantial antioxidant and enzyme inhibitory activities further confirmed by molecular docking studies. This study appraised the use of S. chirayita aerial parts as a potential antioxidant and its therapeutic application in various chronic illnesses including Alzheimer's disease, diabetes, and other skin-related disorders.

Enzymatic and selective production of alkyl α-d-glucopyranosides by the α-glucosyl transfer enzyme derived from Xanthomonas campestris WU-9701

Several alkyl glucosides exhibit various bioactivities. 1-Octyl β-d-glucopyranoside produced by organic synthesis is used as a nonionic surfactant. However, no convenient method has been developed for the selective production of alkyl α-glucosides (α-AGs), such as 1-octyl α-d-glucopyranoside (α-OG). Therefore, we developed a simple method for selective production of α-AGs using the glucosyl transfer enzyme XgtA, (E.C. 3.2.1.20), derived from Xanthomonas campestris WU-9701. When 0.80 M alkyl alcohol and 2.5 units XgtA were incubated in 2.0 mL of 30 mM HEPES-NaOH buffer (pH 8.0) containing 1.2 M maltose at 45 °C, a specific α-AG corresponding to each alkyl alcohol (C2-C10) was detected. Under the standard conditions, we examined the selective production of α-OG from 1-octanol and maltose using XgtA. The reaction product was isolated and identified as α-OG via 1H nuclear magnetic resonance and nuclear overhauser effect spectroscopy analyses. No other glucosylated products, such as maltotriose, were detected in the reaction mixture. Under the standard conditions at 45 °C for 96 h, 243 mM α-OG (71 g/L) was produced in one batch production. Moreover, the addition of glucose isomerase to the reaction mixture decreased the concentration of glucose released via the reaction and increased the amount of α-OG produced; 359 mM α-OG (105 g/L) was maximally produced at 96 h. In conclusion, this study demonstrates the selective production of α-AGs using a simple enzymatic reaction, and XgtA has the potential to selectively produce various α-AGs.

Deciphering Molecular Aspects of Potential α-Glucosidase Inhibitors within Aspergillus terreus: A Computational Odyssey of Molecular Docking-Coupled Dynamics Simulations and Pharmacokinetic Profiling

Hyperglycemia, as a hallmark of the metabolic malady diabetes mellitus, has been an overwhelming healthcare burden owing to its high rates of comorbidity and mortality, as well as prospective complications affecting different body organs. Available therapeutic agents, with α-glucosidase inhibitors as one of their cornerstone arsenal, control stages of broad glycemia while showing definitive characteristics related to their low clinical efficiency and off-target complications. This has propelled the academia and industrial section into discovering novel and safer candidates. Herein, we provided a thorough computational exploration of identifying candidates from the marine-derived Aspergillus terreus isolates. Combined structural- and ligand-based approaches using a chemical library of 275 metabolites were adopted for pinpointing promising α-glucosidase inhibitors, as well as providing guiding insights for further lead optimization and development. Structure-based virtual screening through escalating precision molecular docking protocol at the α-glucosidase canonical pocket identified 11 promising top-docked hits, with several being superior to the market drug reference, acarbose. Comprehensive ligand-based investigations of these hits' pharmacokinetics ADME profiles, physiochemical characterizations, and obedience to the gold standard Lipinski's rule of five, as well as toxicity and mutagenicity profiling, proceeded. Under explicit conditions, a molecular dynamics simulation identified the top-stable metabolites: butyrolactone VI (SK-44), aspulvinone E (SK-55), butyrolactone I 4''''-sulfate (SK-72), and terrelumamide B (SK-173). They depicted the highest free binding energies and steadiest thermodynamic behavior. Moreover, great structural insights have been revealed, including the advent of an aromatic scaffold-based interaction for ligand-target complex stability. The significance of introducing balanced hydrophobic/polar moieties, like triazole and other bioisosteres of carboxylic acid, has been highlighted across docking, ADME/Tox profiling, and molecular dynamics studies for maximizing binding interactions while assuring safety and optimal pharmacokinetics for targeting the intestinal-localized α-glucosidase enzyme. Overall, this study provided valuable starting points for developing new α-glucosidase inhibitors based on nature-derived unique scaffolds, as well as guidance for prospective lead optimization and development within future pre-clinical and clinical investigations.

BoGH13ASus from Bacteroides ovatus represents a novel α-amylase used for Bacteroides starch breakdown in the human gut

Members of the Bacteroidetes phylum in the human colon deploy an extensive number of proteins to capture and degrade polysaccharides. Operons devoted to glycan breakdown and uptake are termed polysaccharide utilization loci or PUL. The starch utilization system (Sus) is one such PUL and was initially described in Bacteroides thetaiotaomicron (Bt). BtSus is highly conserved across many species, except for its extracellular α-amylase, SusG. In this work, we show that the Bacteroides ovatus (Bo) extracellular α-amylase, BoGH13ASus, is distinguished from SusG in its evolutionary origin and its domain architecture and by being the most prevalent form in Bacteroidetes Sus. BoGH13ASus is the founding member of both a novel subfamily in the glycoside hydrolase family 13, GH13_47, and a novel carbohydrate-binding module, CBM98. The BoGH13ASus CBM98-CBM48-GH13_47 architecture differs from the CBM58 embedded within the GH13_36 of SusG. These domains adopt a distinct spatial orientation and invoke a different association with the outer membrane. The BoCBM98 binding site is required for Bo growth on polysaccharides and optimal enzymatic degradation thereof. Finally, the BoGH13ASus structure features bound Ca2+ and Mn2+ ions, the latter of which is novel for an α-amylase. Little is known about the impact of Mn2+ on gut bacterial function, much less on polysaccharide consumption, but Mn2+ addition to Bt expressing BoGH13ASus specifically enhances growth on starch. Further understanding of bacterial starch degradation signatures will enable more tailored prebiotic and pharmaceutical approaches that increase starch flux to the gut.

Enzymatic properties of alcohol dehydrogenase PedE_M.s. derived from Methylopila sp. M107 and its broad metal selectivity

As an important metabolic enzyme in methylotrophs, pyrroloquinoline quinone (PQQ)-dependent alcohol dehydrogenases play significant roles in the global carbon and nitrogen cycles. In this article, a calcium (Ca2+)-dependent alcohol dehydrogenase PedE_M.s., derived from the methylotroph Methylopila sp. M107 was inserted into the modified vector pCM80 and heterologously expressed in the host Methylorubrum extorquens AM1. Based on sequence analysis, PedE_M.s., a PQQ-dependent dehydrogenase belonging to a methanol/ethanol family, was successfully extracted and purified. Showing by biochemical results, its enzymatic activity was detected as 0.72 U/mg while the Km value was 0.028 mM while employing ethanol as optimal substrate. The activity of PedE_M.s. could be enhanced by the presence of potassium (K+) and calcium (Ca2+), while acetonitrile and certain common detergents have been found to decrease the activity of PedE_M.s.. In addition, its optimum temperature and pH were 30°C and pH 9.0, respectively. Chiefly, as a type of Ca2+-dependent alcohol dehydrogenase, PedE_M.s. maintained 60-80% activity in the presence of 10 mM lanthanides and displayed high affinity for ethanol compared to other PedE-type enzymes. The 3D structure of PedE_M.s. was predicted by AlphaFold, and it had an 8-bladed propeller-like super-barrel. Meanwhile, we could speculate that PedE_M.s. contained the conserved residues Glu213, Asn300, and Asp350 through multiple sequence alignment by Clustal and ESpript. The analysis of enzymatic properties of PedE_M.s. enriches our knowledge of the methanol/ethanol family PQQ-dependent dehydrogenase. This study provides new ideas to broaden the application of alcohol dehydrogenase in alcohol concentration calculation, biosensor preparation, and other industries.

The effect of barium and strontium on activity of glucoamylase QsGH97a from Qipengyuania seohaensis SW-135

Glycoside hydrolases (GHs), the enzymes that break glycosidic bonds, are ubiquitous in the ecosystem, where they perform a range of biological functions. As an interesting glycosidase family, Glycoside hydrolase family 97 (GH97) contains α-glucosidase, α-galactosidase, and glucoamylase. Only ten members of GH97 have been characterized so far. It is critical to explore novel members to elucidate the catalytic mechanism and application potential of GH97 family. In this study, a novel glucoamylase QsGH97a from Qipengyuania seohaensis SW-135 was cloned and expressed in E. coli. Sequence analysis and NMR results show that QsGH97a is classified into GH97a, and adopts inverting mechanism. The biochemical characterization indicates that QsGH97a shows the optimal activity at 50 °C and pH 8.0. Ca²⁺ has little effect on the catalytic activity; however, the activity can be substantially increased by 8-13 folds in the presence of Ba²⁺ or Sr²⁺. Additionally, the metal content of QsGH97a assay showed a high proportion of Sr²⁺. The specific metal activity was initially revealed in glucoamylases, which is not found in other members. These results imply that QsGH97a not only is a new member of GH97, but also has potential for industrial applications. Our study reveals that Ba²⁺ or Sr²⁺ may be involved in the catalytic mechanism of glucoamylase, laying the groundwork for a more complete knowledge of GH97 and its possible industrial application.