Enzymatic synthesis of functional amylosic materials and amylose analog polysaccharides.

Because polysaccharides have very complicated chemical structures constructed by a great diversity of monosaccharide residues and glycosidic linkages, enzymatic approaches have been identified as powerful tools to precisely synthesize polysaccharides as the reactions progress in highly controlled regio- and stereoarrangements. α-Glucan phosphorylase (GP) is one of the enzymes that have acted as catalysts for the practical production of well-defined polysaccharides. GP can catalyze enzymatic polymerization of α-d-glucose 1-phosphate (Glc-1-P) as a monomer from a maltooligosaccharide primer to produce a pure amylose with well-defined structure via the formation of α(1→4)-glycosidic linkages. Here, the author presents methods which achieve the enzymatic synthesis of functional amylosic materials and amylose analog polysaccharides by GP-catalyzed enzymatic polymerization approaches. As the polymerization progresses at the non-reducing end of the primer, it can be conducted using polymeric primers that are modified at the reducing end and covalently attached on suitable polymeric chains. By using such polymeric primers, various amylose-grafted functional materials can be enzymatically synthesized. For example, the detailed protocol for the synthesis of amylose-grafted poly(γ-glutamic acid) is described. GP shows loose specificity for the recognition of substrates, which allows to recognize some monosaccharide 1-phosphates as analog substrates of Glc-1-P. Representatively, the experimental procedure of the GP-catalyzed enzymatic polymerization of α-d-glucosamine 1-phosphate as the analog substrate is presented to synthesize an α(1→4)-linked glucosamine polymer, that is called amylosamine. By means of a similar approach catalyzed by GP, several amylose analog polysaccharides have been obtained.