Carbohydrate transport and phosphorylation by the PTS and their coupling to glycolysis. Carbohydrate transport and phosphorylation by the PTS and their coupling to glycolysis. Carbohydrates are transported and concomitantly phosphorylated by the PTS. The phosphorylated carbohydrate feeds into glycolysis, normally at the glucose-6-P or fructose-6-P level. Two phosphoenolpyruvate molecules are usually formed in glycolysis, one of which is used to drive the transport and initial phosphorylation of the carbohydrate. As a result, the phosphorylation state of the PTS proteins depends on both the concentration of extracellular carbohydrates and the ratio of internal phosphoenolpyruvate and pyruvate. Abbreviations for enzymes (in boldface type) are as follows: Pgi, phosphoglucose isomerase; Pfk, phosphofructokinase; Fba, fructose-1,6-bisphosphate aldolase; Tpi, triose-phosphate isomerase; Gap, glyceraldehyde-3-phosphate dehydrogenase; Pgk, phosphoglycerate kinase; Pgm, phosphoglycerate mutase; Eno, enolase; Pyk, pyruvate kinase. Josef Deutscher et al. Microbiol. Mol. Biol. Rev. 2006; doi:10.1128/MMBR.00024-06