scholarly journals Role of Periplasmic Trehalase in Uptake of Trehalose by the Thermophilic Bacterium Rhodothermus marinus

2008 ◽  
Vol 190 (6) ◽  
pp. 1871-1878
Author(s):  
Carla D. Jorge ◽  
Luís L. Fonseca ◽  
Winfried Boos ◽  
Helena Santos
Keyword(s):  
Kinetic Parameters ◽  
Glucose Transport ◽  
Transport System ◽  
Glucose Transporter ◽  
Thermophilic Bacterium ◽  
Transport Systems ◽  
Uptake System ◽  
Rhodothermus Marinus ◽  
Whole Cells ◽  
Physiological Relevance

ABSTRACT Trehalose uptake at 65°C in Rhodothermus marinus was characterized. The profile of trehalose uptake as a function of concentration showed two distinct types of saturation kinetics, and the analysis of the data was complicated by the activity of a periplasmic trehalase. The kinetic parameters of this enzyme determined in whole cells were as follows: Km = 156 ± 11 μM and V max = 21.2 ± 0.4 nmol/min/mg of total protein. Therefore, trehalose could be acted upon by this periplasmic activity, yielding glucose that subsequently entered the cell via the glucose uptake system, which was also characterized. To distinguish the several contributions in this intricate system, a mathematical model was developed that took into account the experimental kinetic parameters for trehalase, trehalose transport, glucose transport, competition data with trehalose, glucose, and palatinose, and measurements of glucose diffusion out of the periplasm. It was concluded that R. marinus has distinct transport systems for trehalose and glucose; moreover, the experimental data fit perfectly with a model considering a high-affinity, low-capacity transport system for trehalose (Km = 0.11 ± 0.03 μM and V max = 0.39 ± 0.02 nmol/min/mg of protein) and a glucose transporter with moderate affinity and capacity (Km = 46 ± 3 μM and V max = 48 ± 1 nmol/min/mg of protein). The contribution of the trehalose transporter is important only in trehalose-poor environments (trehalose concentrations up to 6 μM); at higher concentrations trehalose is assimilated primarily via trehalase and the glucose transport system. Trehalose uptake was constitutive, but the activity decreased 60% in response to osmotic stress. The nature of the trehalose transporter and the physiological relevance of these findings are discussed.

The influence of shoot and root size on nitrogen uptake in wheat is affected by nitrate affinity in the roots during early growth

2015 ◽  
Vol 42 (12) ◽  
pp. 1179 ◽  
Author(s):  
Jiayin Pang ◽  
Stephen P. Milroy ◽  
Gregory J. Rebetzke ◽  
Jairo A. Palta
Keyword(s):  
Kinetic Parameters ◽  
Root System ◽  
Transport System ◽  
Field Trial ◽  
N Uptake ◽  
Early Growth ◽  
Transport Systems ◽  
Uptake Kinetic ◽  
Influx Rate ◽  
Wheat Genotypes

Shoot and root system size influences N uptake in wheat (Triticum aestivum L.). Previously, we showed that four wheat genotypes with different biomass had similar N uptake at tillering. In the present study, we determined whether the similarity in N uptake in these genotypes was associated with genotypic differences in the affinity of the root system for NO3– uptake. Kinetic parameters of NO3– uptake were measured in hydroponic seedlings of vigorous and nonvigorous early growth wheat genotypes by exposing them to solutions with differing concentrations of K15NO3 for 15 min. In the low concentration range, the high-affinity transport system of the nonvigorous cultivar Janz showed a higher maximum influx rate than the three vigorous lines and a higher affinity than two of the three vigorous lines. At high NO3– concentrations, where the low-affinity transport system was functional, the responsiveness of NO3– uptake to external concentrations was greater in Janz than in the vigorous lines. Both the high- and low-affinity transport systems were inducible. The genotypic variation in the kinetic parameters of NO3– uptake was large enough to offset differences in morphological traits and should be considered in efforts to improve N uptake. In a field trial, the growth and N uptake performance of the four wheat genotypes was investigated over the winter–spring growing season (June–November of 2010). The field trial showed that although early N uptake was disproportionately large relative to biomass accumulation, the differences in uptake at tillering can be changed by subsequent patterns of uptake.

Glucose transport by an arctic and a temperate strain of rhizobia

1991 ◽  
Vol 37 (2) ◽  
pp. 105-109 ◽  
Author(s):  
Pierre C. Bigwaneza ◽  
Danielle Prévost ◽  
Lucien M. Bordeleau ◽  
Hani Antoun
Keyword(s):  
Key Words ◽  
Glucose Transport ◽  
Transport System ◽  
High Energy ◽  
The Arctic ◽  
Transport Systems ◽  
High Energy Phosphate ◽  
Rhizobium Species ◽  
Onobrychis Viciifolia ◽  
Active Mechanism

Glucose transport was studied in two strains of Rhizobium species effective on sainfoin (Onobrychis viciifolia), the arctic strain N31 isolated from Astragalus alpinus and the temperate strain SM2 isolated from sainfoin. The two strains had comparable glucose transport systems with a biphasic kinetics, indicating the presence of a high- and low-affinity transport system. Apparent Km and Vmax values for the high- and low-affinity transport systems were, respectively, 4.7 and 53.4 μM and 12.7 and 58.9 nmol∙min−1∙mg protein−1 with N31 and 2.6 and 72.6 μM and 10.1 and 64.6 nmol∙min−1∙mg protein−1 with SM2. Glucose transport systems were inhibited by 2,4-dinitrophenol, KCN, azide, and N-ethylmaleimide. NaF did not affect glucose transport, while arsenate showed partial inhibition of the low-affinity transport system with strain N31. These results suggest an active mechanism of transport that is dependent on an energized membrane but does not directly utilize high-energy phosphate compounds. In the two strains, glucose transport is constitutive and repressed by succinate, and it is glucose specific. Key words: Arctic, glucose, Rhizobium, symbiosis, transport.

scholarly journals Differential regulation of the HepG2 and adipocyte/muscle glucose transporters in 3T3L1 adipocytes. Effect of chronic glucose deprivation

1990 ◽  
Vol 271 (1) ◽  
pp. 201-207 ◽  
Author(s):  
K M Tordjman ◽  
K A Leingang ◽  
M Mueckler
Keyword(s):  
Glucose Transport ◽  
Glucose Transporter ◽  
Glucose Deprivation ◽  
Transport Systems ◽  
Facilitated Diffusion ◽  
Glucose Starvation ◽  
Transport Activity ◽  
Maximal Increase ◽  
Glut 1 ◽  
Glut 4

Glucose transport in 3T3L1 adipocytes is mediated by two facilitated diffusion transport systems. We examined the effect of chronic glucose deprivation on transport activity and on the expression of the HepG2 (GLUT 1) and adipocyte/muscle (GLUT 4) glucose transporter gene products in this insulin-sensitive cell line. Glucose deprivation resulted in a maximal increase in 2-deoxyglucose uptake of 3.6-fold by 24 h. Transport activity declined thereafter but was still 2.4-fold greater than the control by 72 h. GLUT 1 mRNA and protein increased progressively during starvation to values respectively 2.4- and 7.0-fold greater than the control by 72 h. Much of the increase in total immunoreactive GLUT 1 protein observed later in starvation was the result of the accumulation of a non-functional or mistargeted 38 kDa polypeptide. Immunofluorescence microscopy indicated that increases in GLUT 1 protein occurred in presumptive plasma membrane (PM) and Golgi-like compartments during prolonged starvation. The steady-state level of GLUT 4 protein did not change during 72 h of glucose deprivation despite a greater than 10-fold decrease in the mRNA. Subcellular fractionation experiments indicated that the increased transport activity observed after 24 h of starvation was principally the result of an increase in the 45-50 kDa GLUT 1 transporter protein in the PM. The level of the GLUT 1 transporter in the PM and low-density microsomes (LDM) was increased by 3.9- and 1.4-fold respectively, and the GLUT 4 transporter content of the PM and LDM was 1.7- and 0.6-fold respectively greater than that of the control after 24 h of glucose deprivation. These data indicate that newly synthesized GLUT 1 transporters are selectively shuttled to the PM and that GLUT 4 transporters undergo translocation from an intracellular compartment to the PM during 24 h of glucose starvation. Thus glucose starvation results in an increase in glucose transport in 3T3L1 adipocytes via a complex series of events involving increased biosynthesis, decreased turnover and subcellular redistribution of transporter proteins.

scholarly journals Dapagliflozin: A Once-Daily Oral Therapy Sodium-Glucose Cotransporter-2 Inhibitor for the Treatment of Adult Patients with Type 2 Diabetes

2011 ◽  
Vol 3 ◽  
pp. CMT.S6168 ◽  
Author(s):  
Khalid Jadoon ◽  
Iskandar Idris
Keyword(s):  
Adverse Effects ◽  
Glucose Transport ◽  
Transport System ◽  
Glucose Transporter ◽  
Intestinal Transport ◽  
Selective Inhibition ◽  
Genetic Syndromes ◽  
Glucose Levels ◽  
Glucose Transporter 2 ◽  
Glucose Transport System

The induction of glycosuria using phlorizin, a nonselective inhibitor of renal and intestinal transport was well recognised to lower glucose levels and induce calorie loss in animal models of diabetes. Phlorizin and other similar molecules however were not suitable for clinical use due to adverse effects of non selective inhibition of extra-renal glucose transport system. More recent understanding of the physiology of renal glucose transport system and increased knowledge of rare genetic syndromes of renal glycosuria has resulted in the development of drugs that selectively inhibit the Sodium Glucose Transporter-2 (SGLT2). Among the various agents currently being developed within this drug class, dapagliflozin is the most advanced in clinical development. This article discusses the basic physiology of the SGLT2 transporter system, pharmacokinetics and pharmacodynamic information of dapagliflozin, its efficacy in lowering HbA1c and weight as well as its safety and adverse effects profile. This is discussed based on evidence derived from clinical trials involving a spectrum of patients with diabetes, from drug naïve to individuals already on insulin therapy.

scholarly journals The d-Xylose-Binding Protein, XylF, from Thermoanaerobacter ethanolicus 39E: Cloning, Molecular Analysis, and Expression of the Structural Gene

1998 ◽  
Vol 180 (14) ◽  
pp. 3570-3577 ◽  
Author(s):  
Milutin Erbeznik ◽  
Herbert J. Strobel ◽  
Karl A. Dawson ◽  
Chris R. Jones
Keyword(s):  
Amino Acid ◽  
Binding Proteins ◽  
Binding Protein ◽  
Xylose Isomerase ◽  
Thermophilic Bacterium ◽  
Transport Systems ◽  
Uptake System ◽  
Calculated Molecular Mass ◽  
Thermoanaerobacter Ethanolicus ◽  
High Affinity

ABSTRACT Immediately downstream from the Thermoanaerobacter ethanolicus xylAB operon, comprising genes that encoded-xylose isomerase and d-xylulose kinase, lies a 1,101-bp open reading frame that exhibits 61% amino acid sequence identity to the Escherichia coli d-xylose binding periplasmic receptor, XylF, a component of the high-affinity binding-protein-dependent d-xylose transport. The 25-residue N-terminal fragment of the deduced T. ethanolicus XylF has typical features of bacterial leader peptides. The C-terminal portion of this leader sequence matches the cleavage consensus for lipoproteins and is followed by a 22-residue putative linker sequence rich in serine, threonine, and asparagine. The putative mature 341-amino-acid-residue XylF (calculated molecular mass of 37,069 Da) appears to be a lipoprotein attached to the cell membrane via a lipid anchor covalently linked to the N-terminal cysteine, as demonstrated by metabolic labelling of the recombinant XylF with [14C]palmitate. The induced E. coli avidly bound d-[14C]xylose, yielding additional evidence that T. ethanolicus XylF is thed-xylose-binding protein. On the basis of sequence comparison of XylFs to other monosaccharide-binding proteins, we propose that the sequence signature of binding proteins specific for hexoses and pentoses be refined as (KDQ)(LIVFAG)3IX3(DN)(SGP)X3(GS)X(LIVA)2X2A. Transcription of the monocistronic 1.3-kb xylF mRNA is inducible by xylose and unaffected by glucose. Primer extension analysis indicated that xylF transcription initiates from two +1 sites, both situated within the xylAB operon. Unlike in similar transport systems in other bacteria, the genes specifying the membrane components (e.g., ATP-binding protein and permease) of the high-affinity d-xylose uptake system are not located in the vicinity of xylF in T. ethanolicus. This is the first report of a gene encoding a xylose-binding protein in a gram-positive or thermophilic bacterium.

scholarly journals Renal transport of neutral amino acids. Tubular localization of Na+-dependent phenylalanine- and glucose-transport systems

1984 ◽  
Vol 220 (1) ◽  
pp. 15-24 ◽  
Author(s):  
U Kragh-Hansen ◽  
H Røigaard-Petersen ◽  
C Jacobsen ◽  
M I Sheikh
Keyword(s):  
Glucose Transport ◽  
Transport System ◽  
Membrane Vesicles ◽  
Transport Systems ◽  
Rabbit Kidney ◽  
Outer Cortex ◽  
High Affinity ◽  
Pars Recta ◽  
Pars Convoluta ◽  
Phenylalanine Transport

The transport properties for phenylalanine and glucose in luminal-membrane vesicles from outer cortex (pars convoluta) and outer medulla (pars recta) of rabbit kidney were studied by a spectrophotometric method. Uptake of phenylalanine as well as of glucose by the two types of membrane vesicles was found to be Na+-dependent, electrogenic and stereospecific. Na+-dependent transport of L-phenylalanine by outer-cortical membrane vesicles could be accounted for by one transport system (KA congruent to 1.5 mM). By contrast, in the outer-medullary preparation, L-phenylalanine transport occurred via two transport systems, namely a high-affinity system with K1A congruent to 0.33 mM and a low-affinity system with K2A congruent to 7 mM respectively. Na+-dependent uptake of D-glucose by pars convoluta and pars recta membrane vesicles could be described by single, but different, transport systems, namely a low-affinity system with KA congruent to 3.5 mM and a high-affinity system with KA congruent to 0.30 mM respectively. Attempts to calculate the stoichiometry of the different Na+/D-glucose transport systems by using Hill-type plots revealed that the ratio of the Na+/hexose co-transport probably is 1:1 in the case of pars convoluta and 2:1 in membrane vesicles from pars recta. The Na+/L-phenylalanine stoichiometry of the pars convoluta transporter probably is 1:1. Both the high-affinity and the low-affinity Na+-dependent L-phenylalanine transport system of pars recta membrane vesicles seem to operate with a 1:1 stoichiometry. The physiological importance of the arrangement of low-affinity and high-affinity transport systems along the kidney proximal tubule is discussed.

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 Cytochalasin B as a probe for the two hexose-transport systems in rat L6 myoblasts

1988 ◽  
Vol 251 (1) ◽  
pp. 63-72 ◽  
Author(s):  
S R Chen ◽  
T C Y Lo
Keyword(s):  
Plasma Membrane ◽  
Transport System ◽  
Binding Sites ◽  
Cytochalasin B ◽  
Transport Systems ◽  
Scatchard Analysis ◽  
Hexose Transport ◽  
Whole Cells ◽  
High Affinity ◽  
Binding Data

We have recently demonstrated that two hexose-transport systems are present in undifferentiated rat L6 myoblasts: D-glucose and 2-deoxy-D-glucose are preferentially transported by the high-affinity system, whereas 3-O-methyl-D-glucose is transported primarily by the low-affinity system. Mutant D23 is found to be defective only in the high-affinity hexose-transport system. The low-affinity transport system is much more sensitive to inhibition by cytochalasin B (CB). The present study examines the identity, properties and regulation of the CB-binding sites by measuring CB binding to both whole cells and plasma membrane. Scatchard analysis of the binding data revealed the presence of two CB-binding sites, namely CBH and CBL. These two sites differ not only in their affinity for CB, but their levels can also be differentially altered by various biochemical, physiological and genetic manipulations. CBL resembles the high-affinity hexose-transport system in that it is absent in mutant D23 and is present in larger quantities in glucose-starved cells. Moreover, CB binding to this site is inhibited by D-glucose and 2-deoxy-D-glucose, the preferred substrates of the high-affinity hexose-transport system. On the other hand, CBH is found to be unaltered in mutant D23, which also retains the normal low-affinity hexose-transport system. CBH also resembles the low-affinity transport system in that it is not elevated in glucose-starved cells. Furthermore, binding of CB to this site can be inhibited by 3-O-methyl-D-glucose, the preferred substrate of the low-affinity transport system. It should be noted that 2-deoxy-D-glucose does not have much effect on CBH, and vice versa. Studies with purified membrane preparations indicate that both CB-binding sites are present in similar ratios in the plasma membrane and the low-density microsomal fraction. Plasma-membrane studies also reveal that D-glucose 6-phosphate, but not 2-deoxy-D-glucose 6-phosphate, is very effective in activating CB binding. Data presented suggest that CB binding may be regulated by sugar analogues in an allosteric manner.

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