Catalyzes 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. The branch chain-length distribution of the reaction products shows degree of polymerization (DP) of 5 to 30, with two local maxima at DP 6 and DP 11. Exhibits an alpha-retaining catalytic mechanism. Does not display alpha-galactosidase or pullulanase activity, since melibiose and pullulan are not substrates. Is not able to catalyze the hydrolysis or transglycosylation of maltoheptaose, suggesting that the TK1436 protein contains neither alpha-amylase nor 4-alpha-glucanotransferase activity. Transfers a segment of a (1->4)-alpha-D-glucan chain to a primary hydroxy group in a similar glucan chain. Optimum pH is 7.0. Optimum temperature is 70 degrees Celsius. Is thermostable up to 90 degrees Celsius. Monomer. Up-regulated by maltodextrin. The C-terminus contains two copies of a helix-hairpin-helix (HhH) motif that are dispensable for activity and thermal stability. Belongs to the glycosyl hydrolase 57 family.