Glucan_BSP_ModH catalyzes the elongation of beta-1,2 polyglucose chains of glucan.
Periplasmic Glucan Biosynthesis protein ModH is a glucosyltransferase that catalyzes the elongation of beta-1,2 polyglucose chains of glucan, requiring a beta-glucoside as a primer and UDP-glucose as a substrate. Glucans are composed of 5 to 10 units of glucose forming a highly branched structure, where beta-1,2-linked glucose constitutes a linear backbone to which branches are attached by beta-1,6 linkages. In Escherichia coli, glucans are located in the periplasmic space, functioning as regulator of osmolarity. It is synthesized at a maximum when cells are grown in a medium with low osmolarity. It has been shown to span the cytoplasmic membrane.