Acidic glycosphingolipids, gangliosides are mainly expressed in nervous tissues and cancer cells, and regulate the health of the tissues. We generated mutant mice lacking various gangliosides by knocking out ganglioside synthase genes, and reported that these knockout (KO) mice exhibited various neurodegeneration. As one of roles of gangliosides, it was demonstrated that abnormal construction of lipid rafts due to ganglioside deficiency induced chronic inflammation and neurodegeneration in these KO mice. On the other hand, gangliosides expressed in melanomas and gliomas caused shifts of localization of various molecules into lipid rafts. And shift of molecules into lipid rafts enhanced signals, leading to malignant phenotypes. In this review, we reported how gangliosides play a role in maintaining the integrity of neural tissues and regulating cancer properties, based on our findings.
Glycosyl cations, which have been considered key intermediates for synthetic carbohydrate chemistry since the earliest days of the field, can sometimes act in unexpected and unpredictable ways. A close examination of these cations tells us that some of this behavior relies on well-tuned interactions that allow these cations to avoid undesired or unexpected reactions that would otherwise utilize these glycosyl cations aggressively. This minireview provides selected examples of how glycosyl cations can be “tamed” to favor desirable reactions, particularly for neighboring group participation and SN2-like reactions.
Oligosaccharides are highly flexible molecules with significant degrees of freedom in their structures. To gain insights into the molecular basis of their biological functions, it is important to describe the conformational dynamics of oligosaccharides. The combination of molecular simulations and nuclear magnetic resonance (NMR) spectroscopy is an effective method for quantitatively interpreting the dynamic behaviors of oligosaccharides. In NMR analyses, paramagnetic-tagging of oligosaccharides provides information on their overall conformations; paramagnetism-assisted NMR methods can facilitate the validation of oligosaccharide dynamical structures originally derived from molecular dynamics simulations. Using this approach, the dynamic conformations of a series of sialyl oligosaccharides found in gangliosides and high-mannose-type oligosaccharides involved in the glycoprotein quality control system were revealed. The quantitative descriptions of their conformational spaces also provided the dynamic views of oligosaccharide–lectin interactions, which complemented static insights from crystallographic analyses. Understanding the oligosaccharide–lectin binding process enables the design of oligosaccharides with enhanced affinity and specificity for target proteins.
The recombinant production of glycoenzymes plays a significant role in industrial biocatalysis. The selection of an expression system which allows the high-level production of recombinant glycoenzymes using extracellular and intracellular expression, and the need for correct protein folding make Gram-positive bacteria interesting alternatives to the commonly used Gram-negative expression host Escherichia coli. In this overview we summarize recent approaches using Gram-positive bacteria as cell factories for the recombinant production of glycoenzymes, with a special focus on the optimization of glycoprotein production in lactic acid bacteria.
Endo-β-N-acetylglucosaminidases (ENGases) are glycoside hydrolases that are commonly used for glycan analysis of glycoproteins. Recently, ENGases have emerged as promising tools for glycoprotein remodeling, especially in synthesizing biotherapeutic products. Furthermore, cytosolic ENGase has been reported to cause serious symptoms of a rare genetic disorder (NGLY1-deficiency). As a tool for further study of ENGases, a pentasaccharide derivative (MM3D) was synthesized to determine the hydrolytic activity of ENGases by a fluorescence-quenching-based assay system. We succeeded in measuring the hydrolytic activities of ENGases belonging to the glycosyl hydrolase family 85, and investigated the inhibitory activities of known inhibitors. We confirmed that this assay system was suitable for high-throughput screening for inhibitors of human ENGase that have a potential to treat NGLY1-deficiency.