Characterization of substrate and product specificity of the purified recombinant glycogen branching enzyme of Rhodothermus obamensis - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Biochimica et Biophysica Acta (BBA) - General Subjects Année : 2013

Characterization of substrate and product specificity of the purified recombinant glycogen branching enzyme of Rhodothermus obamensis

Résumé

Background: Glycogen and starch branching enzymes catalyze the formation of alpha(1 -> 6) linkages in storage polysaccharides by rearrangement of preexisting alpha-glucans. This reaction occurs through the cleavage of alpha(1 -> 4) linkage and transfer in alpha(1 -> 6) of the fragment in non-reducing position. These enzymes define major elements that control the structure of both glycogen and starch. Methods: The kinetic parameters of the branching enzyme of Rhodothermus obamensis (RoBE) were established after in vitro incubation with different branched or unbranched alpha-glucans of controlled structure. Results: A minimal chain length of ten glucosyl units was required for the donor substrate to be recognized by RoBE that essentially produces branches of DP 3-8. We show that RoBE preferentially creates new branches by intermolecular mechanism. Branched glucans define better substrates for the enzyme leading to the formation of hyper-branched particles of 30-70 nm in diameter (dextrins). Interestingly, RoBE catalyzes an additional alpha-4-glucanotransferase activity not described so far for a member of the GH13 family. Conclusions: RoBE is able to transfer alpha(1 -> 4)-linked-glucan in C4 position (instead of C6 position for the branching activity) of a glucan to create new alpha(1 -> 4) linkages yielding to the elongation of linear chains subsequently used for further branching. This result is a novel case for the thin border that exists between enzymes of the GH13 family. General significance: This work reveals the original catalytic properties of the thermostable branching enzyme of R. obamensis. It defines new approach to produce highly branched alpha-glucan particles in vitro. (C) 2012 Elsevier B.V. All rights reserved.

Dates et versions

hal-01268245 , version 1 (04-02-2016)

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Xavier Roussel, Christine Lancelon-Pin, Anders Vikso-Nielsen, Agnès Rolland-Sabaté, Florent Grimaud, et al.. Characterization of substrate and product specificity of the purified recombinant glycogen branching enzyme of Rhodothermus obamensis. Biochimica et Biophysica Acta (BBA) - General Subjects, 2013, 1830 (1), pp.2167 - 2177. ⟨10.1016/j.bbagen.2012.09.022⟩. ⟨hal-01268245⟩
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