Carboxy-terminated maltooligosaccharides are expected as cross-linking agent for condensation reaction with other biopolymers. As enzymatic glycosylation progresses regio- and stereoselectively, it is useful for synthesis of fanctional saccharide materials with well-defined structure. Phosphorylase catalyzes glucosylation of α-D-glucose 1-phosphate (Glc-1-P) and maltooligosaccharide as a glycosyl donor and glycosyl acceptor, respectively. As this enzyme shows weak specificity for the recognition of the substrate structures, we already reported that thermostable phosphorylase (from Aquifex aeolicus VF5)-catalyzed glucuronylation using α-D-glucuronic acid 1-phosphate (GlcA-1-P) as a glycosyl donor. In this study, we synthesized carboxy-terminated maltooligosaccharide (GlcA-Glcn-GlcCOONa) by chemoenzymatic approach including the glucuronylation. Oxidation of the reducing end of maltoheptaose was first performed using hypoiodous acid. Introduction of a glucuronic acid residue at the non-reducing end of the oxidized maltooligosaccharide (Glc6-GlcCOONa) was then performed by the phosphorylase-catalyzed glucuronylation using GlcA-1-P. The MALDI-TOF MS of the product indicated that the enzymatic glucuronylation took place accompanied with the enzymatic disproportionation of Glc6-GlcCOONa to give GlcA-Glcn-GlcCOONa with varying degrees of polymerization.

Chemoenzymatic synthesis of carboxy-terminated maltooligosaccharides as cross-linking agent

2019 Fall National Meeting

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