Schematic pathway for metabolism of maltose to anaerobic fermentation end products. A plus sign in a circle and a minus sign in a circle indicate metabolites that activate and inhibit dehydrogenase activities in L. lactis, respectively. MP, maltose phosphorylase; GK, glucokinase; PTA, phosphotransacetylase; ACK, acetate kinase; GAP, glyceraldehyde 3-phosphate; DHAP, dihydroxyacetone phosphate; CoA, coenzyme A.