Different degradation pathways for glucose and fructose in Rhodopseudomonas capsulata

Abstract

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.

Transport of D-glucose in Clostridium thermocellum ATCC-27405.

“…They were broken by vigorous agitation in the presence of glass beads (Sigma Co., Type I, 75-100 microns) in a Vortes mixer (iii) Glucokinase and PEP phosphotransferase activities. The glucokinase activity was determined essentially as described by CoNRAD and SCHLEGEL (12). The reaction mixture with the cell free extract was preincubated at 50° for 4 min before the reaction was started by the addition of the substrate.…”

Fructose and mannose metabolism in Aeromonas hydrophila: identification transport systems and catabolic pathways

“…Membranes Phosphoglucose isomerase and fructose-1,6-bisphosphate aldolase were present in fructose-grown cells as in mannose-grown cells. In addition, an inducible PFM activity (Conrad & Schlegel, 1977), an unusual enzyme converting fructose 1-phosphate to fructose 6-phosphate, was detected in extracts induced by fructose and mannose (Table 3). …”

“…Specific activities were expressed as nmol substrate consumed min-' (mg protein)-' and represented means of at least three determinations. Activities of the following enzymes were assayed as described in previous publications : 6-phosphofructokinase (6-PFK) and 1-PFK (Baumann & Baumann, 1975), 6-phosphogluconate dehydratase and 2-keto-3-deoxy-6-phosphogluconate (KDPG) aldolase (Lessie & Neidhart, 1967), phosphofructomutase (PFM), phosphoglucose isomerase, fructose-l,6-bisphosphatase and fructose-1,6-bisphosphate aldolase (Conrad & Schlegel, 1977), and glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase (Conrad & Schlegel, 1977).…”

An Alternative Pathway for the Degradation of Endogenous Fructose during the Catabolism of Sucrose in Rhodopseudomonas capsulata

“…The filters were washed with 10 ml ice-cold mineral medium and placed in 15 ml toluene/ethanol scintillation cocktail. The radioactivity was measured as described by Conrad & Schlegel (1977a). Cell protein was determined by the method of Schmidt, Liaaen-Jensen 8c Schlegel (1963).…”

“…The preparation of bacterial extracts and the enzyme assays were done as described by Conrad & Schlegel(1977a). Sucrase activity was measured using a mixture similar to that for the fructokinase (EC 2.7.1 .4) assay, with fructose replaced by sucrose.…”