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Journal of Glycobiology | ISSN: 2168-958X | Volume 7
Glycobiology & Glycoproteomics
5th International Conference on
&
August 27-28, 2018 | Toronto, Canada
Molecular Biology & Nucleic Acids
3rd International Conference on
Enzymes as powerful biocatalysts for precision synthesis of oligo and polysaccharides
Oligo- and polysaccharides have complicated structures because of the structurally different monosaccharide units and
differences in stereo- and rearrangements of glycosidic bonds. Various structures of such substances in nature exhibit
several functions in host organisms, and a subtle change in the monosaccharide structure and the type of glycosidic linkage
exerts a profound effect on their properties and functions. Accordingly, the synthesis of well-defined non-natural oligo- and
polysaccharides has attracted significant attention. Enzymes are identified as powerful biocatalysts to precisely synthesize oligo-
and polysaccharides because enzymatic reactions using glycosyl substrates are progressed with regio- and stereocontrolled
fashions in glycosidic linkage formation without the use of protective groups. Phosphorylase, which catalyzes phosphorolysis of
α-(1→4)-glucans at a non-reducing end in the presence of inorganic phosphate, producing α-D-glucose 1-phosphate (Glc-1-P),
is one of the enzymes that are practically used as the catalyst for synthesis of oligo- and polysaccharides with a well-defined
structure. Because by means of the reversibility of the phosphorolytic reaction, phosphorylase catalyzes successive glucosylation
using Glc-1-P as a glycosyl donor (monomer) and a maltooligosaccharide as a glycosyl acceptor (primer) as the polymerization
to produce -(1→4)-glucans, that is, amylose with liberating inorganic phosphate (Fig1). As this enzyme shows loose specificity
for the recognition of substrates, it recognizes several analogue substrates of Glc-1-P as glycosyl donors in glycosylations to give
non-natural oligo- and polysaccharides. For example, α-D-glucosamine (GlcN-1-P) and α-D-glucuronic acid 1-phosphates
have been used as glycosyl donors in phosphorylase-catalyzed enzymatic glucosaminylation and glucuronidation to give
non-natural basic and acidic oligosaccharides having glucosamine and glucuronic acid residues at the non-reducing end,
respectively. Phosphorylase isolated from thermophilic bacteria, Aquifex aerolicus VF5, catalyzes enzymatic polymerization
of GlcN-1-P as a monomer from maltotriose primer. The enzymatic reaction was accelerated in ammonia buffer containing
Mg2+ ion, owing to the precipitation of inorganic phosphate, giving non-natural amino polysaccharide, which corresponded
to chitosan stereoisomer.
Biography
Jun-ichi Kadokawa received his Ph.D. in 1992. He then joined Yamagata University as a Research Associate. From 1996 to 1997, he worked as a visiting scientist
at the Max-Planck-Institute for Polymer Research in Germany. In 1999, he became an Associate Professor at Yamagata University and moved to Tohoku University
in 2002. He was appointed as a Professor of Kagoshima University in 2004. His research interests focus on polysaccharide materials. He received the Award for
Encouragement of Research in Polymer Science (1997) and the Cellulose Society of Japan Award (2009). He has published more than 200 papers in academic
journals.
Jun-ichi Kadokawa
Kagoshima University, Japan
Jun-ichi Kadokawa, J Glycobiol 2018, Volume 7
DOI: 10.4172/2168-958X-C1-010