SAXS Conformational Tracking of Amylose Synthesized by Amylosucrases

• Published in: Biomacromolecules Vol. 14; no. 1; pp. 232 - 239
• Main Authors: Roblin, P, Potocki-Véronèse, G, Guieysse, D, Guerin, F, Axelos, M.A.V, Perez, J, Buleon, A
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 14.01.2013
• Subjects: Amylose - analysis; Amylose - chemical synthesis; Analytical, structural and metabolic biochemistry; Applied sciences; Biological and medical sciences; Chemical Sciences; Crystallography, X-Ray - methods; Enzymes and enzyme inhibitors; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Glucosyltransferases - analysis; Glucosyltransferases - chemical synthesis; Molecular Conformation; Natural polymers; Physicochemistry of polymers; Polymers; Protein Structure, Secondary; Scattering, Small Angle; Starch and polysaccharides; Transferases; Sucrose; Enzyme; Transferases; In situ; Glycosyltransferases; Small angle X ray scattering; Experimental study; Solution polymerization; Amylose; Oside polymer; Hexosyltransferases; Amylosucrase; Conformation; Enzymatic reaction
• ISSN: 1525-7797; 1526-4602
• DOI: 10.1021/bm301651y

Amylose, a linear polymer of α(1,4)-linked glucosyl units and a major constituent of starch granules, can also be enzymatically synthesized in vitro from sucrose by bacterial amylosucrases. Depending on the initial sucrose concentration and the enzyme used, amylose oligomers (or polymers) are formed and self-associate during synthesis into various semicrystalline morphologies. This work describes for the first time a synchrotron SAXS study of the structure in solution of two amylosucrases, namely, NpAS and the thermostable DgAS, under conditions of polymer synthesis and, simultaneously, the amylose conformation. The structure in solution of both amylosucrases during the reaction was shown to be similar to the known crystallographic structures. The conformation of amylose produced at an early stage consists of a mixture of wormlike chains and double helical cylindrical structures. In the case of NpAS, in a second stage, individual double helices pack into clusters before crystallizing and precipitating. Amylose produced by DgAS never self-associates in such clusters due to the higher temperature used for amylose synthesis. All the dimensions determined for wormlike chains and cylindrical conformations at different times of NpAS synthesis are in very good agreement with structural features usually observed on gels of amylose extracted from starch. This provides new insights in understanding the mechanisms of amylose gelation.