Escherichia coli trehalose-6-phosphate synthase is part of the glycosyl transferase family 20, the retaining glycosyl transferases. It is able to catalyse the condensation between Glucose-6-phosphate and UDP-glucose to form trehalose-6-phosphate, an important metabolite for many bacteria and plants. Interest in the enzyme stems both from the study of the unusual reaction mechanism and the fact that it plays a key role in bacterial cell wall synthesis in M. tuberculosis, so is a possible target for antibiotics. It displays sequence and structural identity with the glycogen phosphorylases in particular, suggesting a common mechanism and evolutionary origin. Also found to be similar is the pseudo-glycosyltransferase VldE involved in validoxylamine A 7'-phosphate synthesis.