title: In vitro synthesis of hyperbranched α-glucans using a biomimetic enzymatic toolbox.
abstract: Glycogen biosynthesis requires the coordinated action of elongating and branching enzymes, of which the synergetic action is still not clearly understood. We have designed an experimental plan to develop and fully exploit a biomimetic system reproducing in vitro the activities involved in the formation of α(1,4) and α(1,6) glycosidic linkages during glycogen biosynthesis. This method is based on the use of two bacterial transglucosidases, the amylosucrase from  Neisseria polysaccharea  and the branching enzyme from  Rhodothermus obamensis . The α-glucans synthesized from sucrose, a low cost agroresource, by the tandem action of the two enzymes, have been characterized by using complementary enzymatic, chromatographic, and imaging techniques. In a single step, linear and branched α-glucans were obtained, whose proportions, morphology, molar mass, and branching degree depended on both the initial sucrose concentration and the ratio between elongating and branching enzymes. In particular, spherical hyperbranched α-glucans with a controlled mean diameter (ranging from 10 to 150 nm), branching degree (from 10 to 13%), and weight-average molar mass (3.7 × 10(6) to 4.4 × 10(7) g.mol(-1)) were synthesized. Despite their structure, which is similar to that of natural glycogens, the mechanisms involved in their in vitro synthesis appeared to be different from those involved in the biosynthesis of native hyperbranched α-glucans.
authors: Université de Toulouse, INSA, UPS, INP, LISBP, 135 Avenue de Rangueil, Toulouse, France.
authors: Florent
authors: F
authors: Grimaud
authors: Christine
authors: C
authors: Lancelon-Pin
authors: Agnès
authors: A
authors: Rolland-Sabaté
authors: Xavier
authors: X
authors: Roussel
authors: Sandrine
authors: S
authors: Laguerre
authors: Anders
authors: A
authors: Viksø-Nielsen
authors: Jean-Luc
authors: JL
authors: Putaux
authors: Sophie
authors: S
authors: Guilois
authors: Alain
authors: A
authors: Buléon
authors: Christophe
authors: C
authors: D'Hulst
authors: Gabrielle
authors: G
authors: Potocki-Véronèse
mesh_terms: D015061:1,4-alpha-Glucan Branching Enzyme / Q000235:genetics / Q000378:metabolism*; D032701:Biomimetics; D005936:Glucans / Q000138:chemical synthesis* / Q000737:chemistry / Q000648:ultrastructure; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism*; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D009343:Neisseria / Q000201:enzymology*; D045245:Rhodothermus / Q000201:enzymology*; D013213:Starch / Q000378:metabolism
chemical_list: D005936:Glucans; D013213:Starch; D005964:Glucosyltransferases; D015061:1,4-alpha-Glucan Branching Enzyme; C019700:amylosucrase; D005982:Glutathione Transferase