Model for the synthesis of glycogen by the enzymes of the maltose system. Maltose or maltodextrins entering the cell via the ABC maltose/maltodextrin transporter (not shown) are polymerized by MalQ to maltodextrins long enough to become substrates of GlgB, the branching enzyme, to form glycogen. The presence of glucokinase (Glk) supports the formation of long maltodextrins by removing free glucose formed in the MalQ-catalyzed reaction. MalP and MalZ counteract the formation of long dextrins by removing glucose-1-P from the nonreducing ends (MalP) or by removing glucose from the reducing ends (MalZ) of maltodextrins. Thus, mutants lacking MalP or MalZ produce large amounts of glycogen with maltose/maltodextrin as the carbon source in the absence of GlgA.