A Possible Common Activation Site in Na+-Driven Transport Systems. Partial Purification of the Na-Dependent D-Glucose Transport System From Small Intestinal Brush Borders

1977 ◽  
pp. 269-279 ◽  
Author(s):  
G. Semenza ◽  
C. Tannenbaum ◽  
M. Kessler ◽  
G. Toggenburger ◽  
L. Wahlgren
Keyword(s):  
Glucose Transport ◽  
Transport System ◽  
Transport Systems ◽  
Partial Purification ◽  
Glucose Transport System ◽  
Brush Borders ◽  
Small Intestinal ◽  
Activation Site

Uptake of D-glucose and L-proline by oligotrophic and heterotrophic marine bacteria

1980 ◽  
Vol 26 (4) ◽  
pp. 454-459 ◽  
Author(s):  
Y. Akagi ◽  
N. Taga
Keyword(s):  
Glucose Transport ◽  
Transport System ◽  
Marine Bacteria ◽  
Heterotrophic Bacterium ◽  
Kinetic Studies ◽  
Transport Systems ◽  
Proline Transport ◽  
Oligotrophic Bacterium ◽  
Glucose Transport System ◽  
Broad Specificity

The transport systems of the oligotrophic bacterium 486 for D-glucose and L-proline have been compared with those of the heterotrophic bacterium RP-303. Kinetic studies demonstrated that the rates of D-glucose and L-proline uptake by the two organisms were saturable processes. The apparent Km values of strain 486 for D-glucose and L-proline were 13.0 μM and 0.2 μM, respectively, whereas those of strain RP-303 were 3.2 μM for D-glucose and 1.8 μM for L-proline. Competition studies indicated that the D-glucose transport system of each bacterium was highly specific for D-glucose. The L-proline transport system of the oligotrophic bacterium 486 had a broad specificity, whereas that of the heterotrophic bacterium RP-303 had a narrow one.

scholarly journals The regulation of transport of glucose, gluconate and 2-oxogluconate and of glucose catabolism in Pseudomonas aeruginosa

1976 ◽  
Vol 154 (3) ◽  
pp. 659-668 ◽  
Author(s):  
P H. Whiting ◽  
M Midgley ◽  
E A. Dawes
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Glucose Transport ◽  
Transport System ◽  
Glucose Concentration ◽  
Glucose Dehydrogenase ◽  
Threshold Concentration ◽  
Transport Systems ◽  
Residual Concentration ◽  
Catabolic Enzymes ◽  
Glucose Transport System

1. The induction by glucose and gluconate of the transport systems and catabolic enzymes for glucose, gluconate and 2-oxogluconate was studied with Pseudomonas aeruginosa PAO1 growing in a chemostat under conditions of nitrogen limitation with citrate as the major carbon source. 2. In the presence of a residual concentration of 30mM-citrate an inflowing glucose concentration of 6-8 mM was required to induce the glucose-transport system and associated catabolic enzymes. When the glucose concentration was raised to 20mM the glucose-transport system was repressed, but the transport system for gluconate, and at higher glucose concentrations, that for 2-oxogluconate, were induced. No repression of the glucose-catabolizing enzymes occurred at the higher inflowing glucose concentrations. 3. In the presence of 30mM-citrate no marked threshold concentration was required for the induction of the gluconate-transport system by added gluconate. 4. In the presence of 30mM-citrate and various concentrations of added glucose and gluconate, the activity of the glucose-transport system accorded with the proposal that a major factor concerned in the repression of this system was the concentration of gluconate, produced extracellularly by glucose dehydrogenase. 5. This proposal was supported by chemostat experiments with mutants defective in glucose dehydrogenase. Such mutants showed no repression of the glucose-transport system by high inflowing concentrations, but with a mutant apparently defective only in glucose dehydrogenase, the addition of gluconate caused repression of the glucose-transport system. 6. Studies with the mutants showed that both glucose and gluconate can induce the enzymes of the Entner-Doudoroff system, whereas for the induction of the gluconate-transport system glucose must be converted into gluconate.

scholarly journals Testing transport models and transport data by means of kinetic rejection criteria

1989 ◽  
Vol 260 (3) ◽  
pp. 885-891 ◽  
Author(s):  
R M Krupka
Keyword(s):  
Experimental Data ◽  
Kinetic Analysis ◽  
Glucose Transport ◽  
Transport System ◽  
Reaction Scheme ◽  
Transport Systems ◽  
Choline Transport ◽  
Carrier Model ◽  
Glucose Transport System ◽  
General Relations

In the case of a transport system obeying Michaelis-Menten kinetics, completely general relationships are shown to exist between the final ratio of internal and external substrate concentrations, alpha, and the V/Km ratios found in zero-trans-entry, zero-trans-exit and equilibrium-exchange experiments (where V is a maximum substrate flux and Km a substrate half-saturation constant). The proof depends on a new method of derivation proceeding from the form of the experimental data rather than, as has been the practice in kinetic analysis, from a hypothetical reaction scheme. These general relationships, which will be true of all mechanisms giving rise to a particular type of behaviour (here Michaelis-Menten kinetics), provide a test for internal consistency in a set of experimental data. Other relationships, which are specific, can be derived from individual reaction schemes, with the use of traditional procedures in kinetic analysis. The specific relationships include constants for infinite trans entry and exit in addition to constants involved in the general relationships. In conjunction, the general and specific relationships provide a stringent test of mechanism. A set of results that fails to satisfy the general relationships must be rejected; here systematic error or unexpected changes in the transport system in different experiments may have distorted the calculated constants, or the system may not actually obey Michaelis-Menten kinetics. Results in accord with the general relationships, on the other hand, can be applied in specific tests of mechanism. The usefulness of the theorem is illustrated in the cases of the glucose-transport and choline-transport systems of erythrocytes. Experimental results taken from several studies in the literature, which were in accord with hyperbolic substrate kinetics, had previously been shown to disagree with relationships derived for the carrier model, and the model was rejected. The new analysis shows that the data violated the general relationships and therefore cannot decide the issue. More recent results on the glucose-transport system satisfy the general relations and agree with the carrier model.

Modulation of glucose transport by parathyroid hormone and insulin in UMR 106–01, a clonal rat osteogenic sarcoma cell line

1995 ◽  
Vol 14 (2) ◽  
pp. 263-275 ◽  
Author(s):  
D M Thomas ◽  
S D Rogers ◽  
M W Sleeman ◽  
G M Pasquini ◽  
F R Bringhurst ◽  
...  
Keyword(s):  
Parathyroid Hormone ◽  
Cell Line ◽  
Glucose Transport ◽  
Transport System ◽  
Osteogenic Sarcoma ◽  
Regulatory Subunit ◽  
Sarcoma Cell ◽  
Sarcoma Cell Line ◽  
Glucose Transport System ◽  
Umr 106

ABSTRACT This study characterizes the actions of insulin and parathyroid hormone (PTH) on the glucose transport system in the rat osteogenic sarcoma cell line UMR 106–01, which expresses a number of features of the osteoblast phenotype. Using [1,2-3H]2-deoxyglucose (2-DOG) as a label, UMR 106–01 cells were shown to possess a glucose transport system which was enhanced by insulin. In contrast, PTH influenced glucose transport in a biphasic manner with a stimulatory effect at 1 h and a more potent inhibitory effect at 16 h on basal and insulin-stimulated 2-DOG transport. To explore the mechanism of PTH action, a direct agonist of cAMP-dependent protein kinase (PKA) was tested. 8-Bromo-cAMP had no acute stimulatory effect but inhibited basal and insulin-stimulated 2-DOG transport at 16 h. This result suggested that the prolonged, but not the acute, effect of PTH was mediated by the generation of cAMP. Further studies with the cell line UMR 4–7, a UMR 106–01 clone stably transfected with an inducible mutant inactive regulatory subunit of PKA, confirmed that the inhibitory but not the stimulatory effect of PTH was mediated by the PKA pathway. Northern blot data indicated that the prolonged inhibitory effects of PTH and 8-bromo-cAMP on glucose transport were likely to be mediated in part by reduction in the levels of GLUT1 (HepG2/brain glucose transporter) mRNA.

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