Synthesizes trehalose from ADP-glucose and glucose. Has a much lower activity toward UDP-glucose and GDP-glucose. The reaction is reversible, the equilibrium strongly favors trehalose synthesis (By similarity). an NDP-alpha-D-glucose + D-glucose = a ribonucleoside 5'-diphosphate + alpha,alpha-trehalose + H(+) Homodimer. Belongs to the glycosyltransferase group 1 family. Glycosyltransferase 4 subfamily.