Abstract
Abstract Glycogen is a natural polysaccharide with a dendrimer structure, in which glucose is frequently branched and polymerized. Functionalizing the numerous non-reducing ends on the molecular surface of glycogen could be expected to enable its use in various fields. We developed a method for enzymatically synthesizing a suitable form of glycogen from sucrose by using sucrose phosphorylase and branching enzyme, both of which belong to the α-amylase family, as well as glucan phosphorylase. We refer to this enzymatically synthesized glycogen as the glucan dendrimer (GD). We then selectively modified the non-reducing ends on the surface of GD particles by using the reaction of glucan phosphorylase with various hexose 1-phosphates. Modifying the non-reducing ends of GD with glucuronic acid or glucosamine added negative and positive charges to the GD particles. In addition, we found that glucuronic acid and/or glucosamine residues at the non-reducing ends can be used to covalently conjugate functional substances, such as sugar chains, proteins, and peptides to the surface of GD particles. GD and modification of its non-reducing ends represent versatile platforms for pharmaceutical applications of polysaccharides.
Highlights
Glycogen is a highly branched glucose polysaccharide that serves as a form of energy storage in animals and bacteria
We developed a method for enzymatically synthesizing a suitable form of glycogen from sucrose by using sucrose phosphorylase and branching enzyme, both of which belong to the α-amylase family, as well as glucan phosphorylase
The glycogen-like polysaccharide synthesized by this method was designated a glucan dendrimer (GD) because it is a spherical, highly branched glucan composed of α-1,4/α-1,6 bonds
Summary
Glycogen is a highly branched glucose polysaccharide that serves as a form of energy storage in animals and bacteria. The molecular surface of glycogen has numerous nonreducing ends. We hypothesized that functionalizing these ends could enable various applications of glycogen in the production of conventional food and cosmetics and pharmaceuticals, among other fields. We introduce our research on the enzymatic synthesis of glycogen-like polysaccharides with tightly controlled molecular weight and particle size and on the technique for selectively modifying their non-reducing ends. AqGP, glucan phosphorylase from Aquifex aeolicus; DDS, drug delivery system; GA, glucoamylase; Gal,
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