FIG. 1.

Three pathways for trehalose synthesis in C. glutamicum and Mycobacterium tuberculosis. The otsBA pathway leads to trehalose from glucose 6-phosphate through UDP-glucose and trehalose 6-phosphate as intermediates. In the treYZ pathway, isomerization and hydrolysis of a α(1-4)glucan leads to trehalose. The synthesis of such glucans proceeds in a way fairly similar to the otsBA pathway, with ADP-glucose as the glucosyl donor. Finally, the treS pathway leads to trehalose after isomerization of maltose, when this sugar is available as a carbon source.