<p>Three pathways exist for the biosynthesis of trehalose, an osmoprotectant that in some species is also a precursor of certain cell wall glycolipids. Trehalose synthase, TreS, can interconvert maltose and trehalose, but while the equilibrium favours trehalose, physiological concentrations of trehalose may be much greater than that of maltose, and TreS may act largely in its degradation. This entry describes a domain found only as a C-terminal fusion to TreS proteins. The most closely related proteins outside this family, Pep2 of <taxon tax_id="1902">Streptomyces coelicolor</taxon> and Mak1 of <taxon tax_id="1866">Actinoplanes missouriensis</taxon>, have known maltokinase activity. We suggest this domain acts as a maltokinase and helps drive conversion of trehalose to maltose.</p> Trehalose synthase/probable maltokinase, C-terminal