Monitoring glycosidase activity for clustered sugar substrates, a study on β-glucuronidase

Preparation of hyaluronan oligosaccharides by a prokaryotic beta-glucuronidase: Characterization of free and immobilized forms of the enzyme

Popularity of hyaluronan (HA) in the cosmetics and pharmaceutical industries, led to the investigation and development of new HA-based materials, with enzymes playing a key role. Beta-D-glucuronidases catalyze the hydrolysis of a beta-D-glucuronic acid residue from the non-reducing end of various substrates. However, lack of specificity towards HA for most beta-D-glucuronidases, in addition to the high cost and low purity of those active on HA, have prevented their widespread application. In this study, we investigated a recombinant beta-glucuronidase from Bacteroides fragilis (rBfGUS). We demonstrated the rBfGUS's activity on native, modified, and derivatized HA oligosaccharides (oHAs). Using chromogenic beta-glucuronidase substrate and oHAs, we characterized the enzyme's optimal conditions and kinetic parameters. Additionally, we evaluated rBfGUS's activity towards oHAs of various sizes and types. To increase reusability and ensure the preparation of enzyme-free oHA products, rBfGUS was immobilized on two types of magnetic macroporous bead cellulose particles. Both immobilized forms of rBfGUS demonstrated suitable operational and storage stabilities, and their activity parameters were comparable to the free form. Our findings suggest that native and derivatized oHAs can be prepared using this bacterial beta-glucuronidase, and a novel biocatalyst with enhanced operational parameters has been developed with a potential for industrial use.

Insightful Improvement in the Design of Potent Uropathogenic E. coli FimH Antagonists

Selective antiadhesion antagonists of Uropathogenic Escherichia coli (UPEC) type-1 Fimbrial adhesin (FimH) are attractive alternatives for antibiotic therapies and prophylaxes against acute or recurrent urinary tract infections (UTIs) caused by UPECs. A rational small library of FimH antagonists based on previously described C-linked allyl α-D-mannopyranoside was synthesized using Heck cross-coupling reaction using a series of iodoaryl derivatives. This work reports two new members of FimH antagonist amongst the above family with sub nanomolar affinity. The resulting hydrophobic aglycones, including constrained alkene and aryl groups, were designed to provide additional favorable binding interactions with the so-called FimH "tyrosine gate". The newly synthesized C-linked glycomimetic antagonists, having a hydrolytically stable anomeric linkage, exhibited improved binding when compared to previously published analogs, as demonstrated by affinity measurement through interactions by FimH lectin. The crystal structure of FimH co-crystallized with one of the nanomolar antagonists revealed the binding mode of this inhibitor into the active site of the tyrosine gate. In addition, selected mannopyranoside constructs neither affected bacterial growth or cell viability nor interfered with antibiotic activity. C-linked mannoside antagonists were effective in decreasing bacterial adhesion to human bladder epithelial cells (HTB-9). Therefore, these molecules constituted additional therapeutic candidates' worth further development in the search for potent anti-adhesive drugs against infections caused by UPEC.

A Novel Fluorescent Probe Strategy Activated by β-Glucuronidase for Assisting Surgical Resection of Liver Cancer

Liver cancer is a primary malignant tumor with a very high fatality rate, which has seriously threatened human health and life. In normal hepatocellular lesions, β-glucuronidase (GLU) activity in liver cancer tissues is significantly increased. Therefore, GLU has become one of the important biomarkers of primary liver cancer. Here, a series of fluorescent probes (DCDH, DCDCH₃, DCDOCH₃, and DCDNO₂) for early diagnosis of liver cancer and auxiliary surgical resection were successfully synthesized. Since the electron-withdrawing group -NO₂ connected to the probe DCDNO₂ accelerates the rapid cleavage of the glycosidic bond, DCDNO₂ exhibits superior fluorescence properties that are more sensitive and rapid than the other three probes DCDH, DCDCH₃, and DCDOCH₃ when detecting GLU. DCDNO₂ has been well-applied in real-time fluorescent visualization imaging for the detection of GLU activity in liver cancer cells and tumor tissues. In addition, DCDNO₂ has also been successfully used in the early diagnosis of liver cancer and real-time imaging to guide the surgical resection of liver cancer tumors. Therefore, DCDNO₂ has great potential for development in bioclinical medicine for the early detection and treatment of liver cancer.

Carbohydrate supramolecular chemistry: beyond the multivalent effect

(Hetero)multivalency acts as a multichannel switch that shapes the supramolecular properties of carbohydrates in an intrinsically multifactorial biological context.