(1->2)-beta-D-glucan:(1->2)-beta-D-glucan 2-beta-D-[(1->2)-beta-D-glucano]-transferase (cyclizing and configuration-retaining)
Reaction(IUBMB)
Cyclizes part of a (1->2)-beta-D-glucan chain by formation of a (1->2)-beta-D-glucosidic bond
Comment
This enzyme is the cyclization domain of cyclic beta-1,2-glucan synthase. Enzymes from Brucella abortus and Thermoanaerobacter italicus were characterized. The cyclization domain of cyclic beta-1,2-glucan synthase is flanked by an N-terminal beta-1,2-glucosyltransferase domain (a UDP-alpha-D-glucose-dependent synthase, not EC 2.4.1.391) and a C-terminal beta-1,2-glucoside phosphorylase domain (cf. EC 2.4.1.333), with the former responsible for elongation and the latter for chain length control. The cyclization domain of Thermoanaerobacter italicus cyclizes linear oligosaccharides with a degree of polymerization (DP) of 21 or higher to produce cyclic glucans with DP 17 or higher. The cyclization domain also disproportionates linear beta-1,2-glucooligosaccharides without cycling. The entire cyclic beta-1,2-glucan synthase from Brucella abortus synthesizes cyclic beta-1,2-glucans with DP 17-22.
Inon de Iannino N, Briones G, Tolmasky M, Ugalde RA.
Title
Molecular cloning and characterization of cgs, the Brucella abortus cyclic beta(1-2) glucan synthetase gene: genetic complementation of Rhizobium meliloti ndvB and Agrobacterium tumefaciens chvB mutants.
Interaction network and localization of Brucella abortus membrane proteins involved in the synthesis, transport, and succinylation of cyclic beta-1,2-glucans.
