The phosphoenolpyruvate-dependent sugar phosphotransferase system (sugar PTS), a major carbohydrate active transport system, catalyzes the phosphorylation of incoming sugar substrates concomitantly with their translocation across the cell membrane (PubMed:3129430, PubMed:17158705). The enzyme II complex composed of PtsG and Crr is involved in glucose transport (PubMed:2657735). The non-phosphorylated EIII-Glc is an inhibitor for uptake of certain sugars such as maltose, melibiose, lactose, and glycerol. Phosphorylated EIII-Glc, however, may be an activator for adenylate cyclase. It is an important regulatory protein for cell metabolism (PubMed:789369). Binds 1 zinc ion per glycerol kinase EIIA-Glc dimer. The zinc ion is important for dimerization. Heterodimer with glycerol kinase (glpk). The EIIA domain is phosphorylated by phospho-HPr on a histidyl residue. Then, it transfers the phosphoryl group to the EIIB domain. In mutants defective in enzyme I and histidine-containing phosphate carrier protein (HPr), cells lacking this gene are able to grow on the non-PTS compounds such as glycerol, maltose, melibiose, mannose 6-phosphate, and alpha-glycerol phosphate.