Current Issue


On the origin of galectin and galactose –Part 1–

Jun Hirabayashi / Ryuichiro Suzuki

last updated 2022/06/01 (Glycoforum. 2022 Vol.25 (3), A6)

Galectins are characterized as a group of evolutionarily related proteins having a conserved unique sequence with the ability to bind galactose (rigorously to bind β-galactoside). To date, their diverse biological distributions and functions have been described; however, the origin of galectin has only scarcely been discussed. Curiously, all of them so far investigated lack a signal sequence required for secretion, while they are assumed to function in extracellular spaces, where a vast amount of galectin-binding glycans exist. In fact, regardless of biological species, all the galectins are biosynthesized as “cytosolic proteins”. This suggests that they have intrinsic functions in the cytosol. In this chapter (Part 1), we describe the origin of galectins in light of their cytosolic features. In the following chapter (Part 2), We attempt to discuss the most fundamental issues of galactose, to which all galectins bind, by referring to the origins of monosaccharides and their chirality. ...and more

human milk oligosaccharides

The current manufacturing process and business development of human milk oligosaccharide products

Tetsuro Ujihara / Yanashima Kentaro

last updated 2022/06/01 (Glycoforum. 2022 Vol.25 (3), A7)

Human milk oligosaccharides (HMOs) is the general term for the complex sugar molecules (oligosaccharides) in human breast milk. HMOs are known to be important nutrients for infants because of their great abundance in human colostrum but only trace amount in bovine milk (Fig. 1). Therefore, efficient large-scale production of HMOs is desired to enhance the nutritional value of infant formula. However, HMO production was not easy. Limited numbers of HMOs can be obtained by using natural extraction methods. Although there are several reports on the chemical synthesis of HMOs including 2'-FL, chemical synthesis of HMOs is still inefficient for industrial production purposes. HMOs consist of saccharide moieties with numerous hydroxy groups and should be attached in a stereospecific manner. In order to reduce the synthesis of unexpected byproducts, protection of the hydroxy groups is required, further complicating synthesis. Enzymes which evolved over time can be used to easily produce complicated oligosaccharide chains with position-dependent activity in a stereospecific manner. So, nowadays, most HMOs are produced biologically. ...and more

Chitin and Chitosan

Electrochemical Glycosylation

Toshiki Nokami

last updated 2022/06/01 (Glycoforum. 2022 Vol.25 (3), A8)

Enzymatic methods and chemical methods are two major methodologies for the synthesis of oligosaccharides. The enzymatic method using glycosyl transferase and/or glycosidase is useful for synthesizing oligosaccharides without introduction of protecting groups of hydroxyl groups. By contrast, the chemical method is based on techniques of synthetic organic chemistry. Thus, it is necessary to protect and deprotect reactive functional groups; however, both natural and unnatural oligosaccharides can be prepared. To synthesize these oligosaccharides, a number of building blocks have been developed and a variety of activation methods have also been reported for each of the building blocks. In this article, the electrochemical glycosylation of thioglycosides, which are widely used for chemical synthesis of oligosaccharides, is introduced. Although thioglycosides are stable and easy to handle, they can be selectively activated under electrochemical conditions. ...and more