Reaction: formation of a branched isomalto/malto-polysaccharide from branched malto-oligosaccharides
Other name(s): gtfB (gene name) (ambiguous); gtfD (gene name)
Systematic name: branched (1→4)-α-D-glucan:(1→4)/(1→6)-α-D-glucan 6-α-D-glucosyltransferase
Comments: The enzyme, discovered in several bacterial species, is similar to EC 2.4.1.395, reuteransucrase, yet is not able to act on sucrose. The enzyme, which belongs to the glycoside hydrolase 70 (GH70) family, possesses both hydrolase and transglycosylase activities, cleaving endo α(1→4) linkages from the non-reducing end of maltooligosaccharides and adding the resulting oligosaccharides to the non-reducing end of α-D-glucan chains that terminate with a residue linked by an α-(1→4) linkage, forming an α(1→6) linkage. The enzyme is not able to form successive α(1→6) linkages. Unlike EC 2.4.1.394, 4,6-α-glucanotransferase (linear substrates/linear products), which can only act on linear substrates, this enzyme is able to act on both linear and branched substrates, and can form the branched reuteran type of α-glucan.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Gangoiti, J., van Leeuwen, S.S., Vafiadi, C. and Dijkhuizen, L. The Gram-negative bacterium Azotobacter chroococcum NCIMB 8003 employs a new glycoside hydrolase family 70 4,6-α-glucanotransferase enzyme (GtfD) to synthesize a reuteran like polymer from maltodextrins and starch. Biochim. Biophys Acta 1860 (2016) 1224-1236. [PMID: 26868718]
2. Gangoiti, J., van Leeuwen, S.S., Meng, X., Duboux, S., Vafiadi, C., Pijning, T. and Dijkhuizen, L. Mining novel starch-converting glycoside hydrolase 70 enzymes from the Nestle Culture Collection genome database: the Lactobacillus reuteri NCC 2613 GtfB. Sci. Rep. 7 (2017) 9947. [PMID: 28855510]
3. Pijning, T., Gangoiti, J., Te Poele, E.M., Borner, T. and Dijkhuizen, L. Insights into broad-specificity starch modification from the crystal structure of Limosilactobacillus reuteri NCC 2613 4,6-α-glucanotransferase GtfB. J. Agric. Food Chem. 69 (2021) 13235-13245. [PMID: 34708648]