This entry represents the C-terminal domain found in bacterial 1,4-alpha-glucan branching enzymes, such as TTHA1902 from Thermus thermophilus and TK1436 from Thermococcus kodakarensis, which belong to the glycoside hydrolase family 57 (GH57). These enzymes catalyse the formation of branch points in alpha-glucans by cleavage of an alpha-1,4 glycosidic bond and subsequent transfer of the cleaved-off oligosaccharide to a new alpha-1,6 position. This is an alpha-helical domain composed of a four alpha-helical bundle. It plays a role in the formation of the active-site cleft, being essential for substrate binding and catalysis [1,2].

1: Thermus thermophilus glycoside hydrolase family 57 branching enzyme: crystal structure, mechanism of action, and products formed. Palomo M, Pijning T, Booiman T, Dobruchowska JM, van der Vlist J, Kralj S, Planas A, Loos K, Kamerling JP, Dijkstra BW, van der Maarel MJ, Dijkhuizen L, Leemhuis H; J Biol Chem. 2011;286:3520-3530. PMID:21097495

2: Structural basis for branching-enzyme activity of glycoside hydrolase family 57: structure and stability studies of a novel branching enzyme from the hyperthermophilic archaeon Thermococcus kodakaraensis KOD1. Santos CR, Tonoli CC, Trindade DM, Betzel C, Takata H, Kuriki T, Kanai T, Imanaka T, Arni RK, Murakami MT; Proteins. 2011;79:547-557. PMID:21104698