This enzyme is the cyclization domain of cyclic β-1,2-glucan synthase. Enzymes from Brucella abortus and Thermoanaerobacter italicus were characterized. The cyclization domain of cyclic β-1,2-glucan synthase is flanked by an N-terminal β-1,2-glucosyltransferase domain (a UDP-α-D-glucose-dependent synthase, not EC 2.4.1.391) and a C-terminal β-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 β-1,2-glucooligosaccharides without cycling. The entire cyclic β-1,2-glucan synthase from Brucella abortus synthesizes cyclic β-1,2-glucans with DP 17-22.
The enzyme appears in viruses and cellular organisms
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SYSTEMATIC NAME
IUBMB Comments
(1->2)-beta-D-glucan:(1->2)-beta-D-glucan 2-beta-D-[(1->2)-beta-D-glucano]-transferase (cyclizing and configuration-retaining)
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.
Substrates: the cyclization reaction catalyzed by the Cgs region from positions 991 to 1544 puts an end to the balance between the elongation and phosphorolysis reactions, the linear beta-1,2-glucooligosaccharide protein-linked intermediate is cyclized, and cyclic beta-1,2-glucan (with the appropriate ring size) are released from the protein to the cytoplasm Products: -
Substrates: the cyclization reaction does not occur on the first glucose linked to the protein. The cyclization reaction catalyzed by the enzyme may be an intramolecular transglycosylation reaction during which the nonreducing end of the protein-linked oligosaccharide forms a new glucosidic bond with a glucose of the beta-1,2-sugar backbone, and concomitantly, the aminoacyl-glucose or a glucose-beta-1,2-glucose linkage is cleaved, resulting in the formation and release of cyclic beta-1,2-glucan Products: -
Inon De Iannino, N.; Briones, G.; Tolmasky, M.; Ugalde, R.
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
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