UGGT1 is called a folding sensor protein that recognizes misfolded glycoproteins and selectively glucosylates high-mannose-type glycans on the proteins. However, the use of conventional naturally occurring glycoproteins is insufficient for performing quantitative analysis of the unique properties of UGGT1. We have demonstrated that high-mannose-type glycans, in which various hydrophobic aglycons were introduced, act as good substrates for UGGT1 and are useful analytical tools for its characterization. Moreover, we found that UGGT2, an isoform UGGT1, is also capable of glucosylating these synthetic substrates.
Thioglycosides are widely used in the synthesis of oligosaccharides because they provide high levels of chemical stability and can be chemoselectively activated in a glycosylation reaction. Thioglycosides, however, are prepared from thiols, which can be challenging to use because of their pungent and generally unpleasant odors, as well as their tendency to form disulfides through oxidation, and these factors have effectively limited the application of thioglycosides in organic synthesis. Herein, we describe recent efforts towards the development of odorless methods for the preparation of thioglycosides, as well as an evaluation of their reactivity in the synthesis of oligosaccharides.
Plants have hydroxyproline-rich glycoproteins (HRGPs), containing hydroxyproline residues that are modified by β-arabinooligosaccharides. Several enzymes that catalyze the degradation of β-arabinooligosaccharides in HRGPs were recently discovered in Bifidobacterium longum JCM1217. This review describes three-dimensional structures of one of those enzymes, GH127 β-L-arabinofuranosidase (HypBA1). The X-ray crystal structures of HypBA1 in its apo form and in complex with β-Araf were determined at resolution of 2.2 Å and 2.0 Å respectively. HypBA1 was found to have a novel active center and was suggested to catalyze reactions by an unprecedented mechanism in glycosidases. The proposed reaction mechanism, which was supported by biochemical analysis, uses a Cys residue that coordinates a Zn2+ ion as a nucleophile. There are many homologs of HypBA1 in bacteria, fungi, and plants, and the catalytic residues are highly conserved among them. Therefore, it is predicted that a substantial number of enzymes share a similar reaction mechanism with HypBA1.