title: The use of 6-labeled glucose to assess futile cycling in Escherichia coli.
abstract: To assess the "futile cycle" fructose-6-P leads to fructose-1,6-P2 leads to fructose-6-P in Escherichia coli we have grown the cells on [6-14C]glucose and determined label in the 1-position of glucose obtained from glycogen. In a variety of strains, including a wild type and a mutant without fructose diphosphatase, 1-position labeling was negligible. But there was little label in the 1-position of fructose-1,6-P2 either, which shows that hexose diphosphate and triose-P are not in equilibrium in this organism. Therefore, the lack of 1-position labeling in glycogen does not necessarily indicate lack of futile cycling. One strain, however, a temperature-sensitive glyceraldehyde-3-P dehydrogenase mutant grown at permissive temperature, gave substantial labeling of the 1-position of fructose-1,6-P2. In this strain 1-position labeling in glycogen was low, indicating minimal futile cycling.
mesh_terms: D004926:Escherichia coli / Q000378:metabolism*; D005632:Fructose / Q000378:metabolism*; D006597:Fructose-Bisphosphatase / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D009154:Mutation; D010732:Phosphofructokinase-1 / Q000378:metabolism; D013045:Species Specificity
chemical_list: D005632:Fructose; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D010732:Phosphofructokinase-1; D006597:Fructose-Bisphosphatase; D005947:Glucose