Different degradation pathways for glucose and fructose in Rhodopseudomonas capsulata.
In Rhodopseudomonas capsulata the enzymes of the Entner-Doudoroff pathway and the Embden-Meyerhof pathway have been examined. Fructose-grown cells contained inducible activities of phosphoenolpyruvate-fructosephospho-transferase and 1-phosphofructokinase and only low levels of fructokinase and 6-phosphofructokinase. Although fructose-grown cells contained, in addition, all the enzymes of the Entner-Doudoroff pathway together with fructose-1,6-diphosphatase and phosphoglucose isomerase, the Entner-Doudoroff pathway was not operative in fructose catabolism and served only the degradation of glucose. The functional separation of glucose and fructose catabolism via the Entner-Doudoroff and a modified Embden-Meyerhof pathway, respectively, was confirmed by different approaches: 1. Radiorespirometric experiments with glucose and fructose labelled in positions 1, 2, 3, 3+4 and 6 have been carried out. The pattern of 14CO2-evolution from position-labelled glucose was characteristic for the Entner-Doudoroff pathway, that from position-labelled fructose for the Embden-Meyerhof pathway. 2. In the presence of arsenite up to 50% of glucose- and fructose-carbon was excreted as pyruvate. Using 1-14C-glucose, 86% of the pyruvate was labelled in the carboxyl group, whereas using 1-14C-fructose only 19% of the pyruvate was labelled in the carboxyl group. 3. A glucose-6-phosphate dehydrogenase-deficient mutant was isolated which lacked a functional Entner-Doudoroff pathway but which was unaltered in its ability to grow on fructose.
D005632:Fructose / Q000378:metabolism*; D005636:Fructosephosphates / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D009154:Mutation; D010101:Oxygen Consumption; D010728:Phosphoenolpyruvate; D010732:Phosphofructokinase-1 / Q000032:analysis; D010770:Phosphotransferases / Q000032:analysis; D011773:Pyruvates / Q000096:biosynthesis; D012241:Rhodopseudomonas / Q000201:enzymology*
D005636:Fructosephosphates; D011773:Pyruvates; D005632:Fructose; D010728:Phosphoenolpyruvate; D010770:Phosphotransferases; D010732:Phosphofructokinase-1; D005947:Glucose