Reversibly catalyzes the synthesis and degradation of trehalose from glucose and alpha-D-glucose 1-phosphate. The equilibrium lies in the direction of trehalose synthesis. alpha,alpha-trehalose + phosphate = alpha-D-glucose + alpha-D-glucose 1-phosphate Optimum pH for phosphorolysis of trehalose is 6.7. Stable between pH 6.0 and 7.0. Optimum temperature for phosphorolysis of trehalose is 36 degrees Celsius. Stable below 30 degrees Celsius, activity decreases to 58% of maximum after 3 minutes incubation at 40 degrees Celsius. Homodimer. Expressed in mycelia, stipes and pilei. By heat stress, cold stress and salt stress. Belongs to the glycosyltransferase group 1 family. Glycosyltransferase 4 subfamily.