Amino acid transport in human and in sheep erythrocytes

1980 ◽  
Vol 209 (1176) ◽  
pp. 355-375 ◽  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Kinetic Studies ◽  
Transport Systems ◽  
Acid Transport ◽  
Sheep Erythrocytes ◽  
Neutral Amino Acids ◽  
L System ◽  
Dibasic Amino Acids

Amino acid transport was compared in human and in sheep erythrocytes. Kinetic studies established that human cells have three discrete amino acid transport systems, designated L, Ly + and ASC. The L system is partially stereospecific, with a preference for large neutral amino acids. L-leucine has a threefold lower apparent K m and a twofold smaller V max than D-leucine. Alanine, cysteine and possibly dibasic amino acids are transported by this route, but with a low affinity. The Ly + system is highly stereoselective, and specific for dibasic amino acids, including arginine. The ASC system is Na-dependent and selective for neutral amino acids of intermediate size. It has a particularly low apparent K m for cysteine and is stereospecific. Sheep erythrocytes lack these systems. Instead they possess an additional system (C system) responsible for the transport both of neutral and of dibasic amino acids, with cysteine as the optimal substrate. Although the substrate specificities of the human ASC and sheep C systems are similar, the sheep system does not require Na and has considerably higher apparent K m values. Dibasic amino acid transport (of lysine, but not of arginine) by the C system occurs with a low affinity.

Amino acid transport systems in intestinal brush-border membranes from lepidopteran larvae

1989 ◽  
Vol 257 (3) ◽  
pp. R494-R500 ◽  
Author(s):  
B. Giordana ◽  
V. F. Sacchi ◽  
P. Parenti ◽  
G. M. Hanozet
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Brush Border ◽  
Amino Acid Transport ◽  
Transport Systems ◽  
Acid Transport ◽  
Specific System ◽  
Neutral Amino Acids ◽  
Intestinal Brush Border ◽  
Lepidopteran Larvae

Experiments with intestinal brush-border membrane vesicles from lepidopteran larvae disclosed the occurrence of unique cotransporter proteins that use K+ as the driver cation for the transmembrane transfer of amino acids across the luminal border of midgut enterocytes. Six apical membrane amino acid transport systems have been identified. These systems are 1) a neutral amino acid transporter with a broad spectrum of interactions with most neutral amino acids, which is highly concentrative, strongly K+- and electrical potential-dependent, poorly stereospecific, and recognizes histidine, but not proline, glycine, or alpha-(methylamino)isobutyric acid (MeAIB); 2) a specific system for L-proline; 3) a specific system for glycine with a higher affinity for Na+ than for K+; 4) a specific system for L-lysine, which is dependent on membrane potential, is highly sensitive to external K+, and does not interact with L-arginine or neutral amino acids; 5) a specific K+-dependent process for glutamic acid, which does not recognize aspartic acid; and last, 6) an apparently unique K+- driven mechanism for D-alanine, which is potential-dependent and strongly stereospecific.

Amino acid transport systems of cultured soybean root cells

1975 ◽  
Vol 53 (18) ◽  
pp. 2088-2091 ◽  
Author(s):  
J. King ◽  
Rozina Hirji
Keyword(s):  
Amino Acids ◽  
Glycine Max ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Transport Systems ◽  
Acid Transport ◽  
Root Cells ◽  
Soybean Root ◽  
Neutral Amino Acids ◽  
Glycine Max L

The uptake of 1 μM14C-labelled arginine, glutamate, and alanine by cultured soybean (Glycine max L. cv. Mandarin) root cells was followed for periods up to 4 min at pH 5.5 in the presence of a 10 μM concentration of other amino compounds. From the degree of competition between 14C-labelled and unlabelled amino acids a number of uptake systems for basic, acidic, and neutral amino acids were identified, and a number of problems associated with amino acid transport in soybean cells were uncovered.

Evidence for Distinct Amino Acid Transport Systems in Cultured Tobacco Cells

1978 ◽  
Vol 33 (9-10) ◽  
pp. 641-645 ◽  
Author(s):  
Jochen Berlin ◽  
Ulrich Mutert
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Aspartic Acid ◽  
Cell Lines ◽  
Amino Acid Transport ◽  
Transport Systems ◽  
Tobacco Cell ◽  
Acid Transport ◽  
Basic Amino Acids ◽  
Neutral Amino Acids

Abstract It is shown by competition experiments that tobacco cell lines have distinct transport systems for ʟ-amino acids. For all tested amino acids the Lineweaver-Burk plots were diphasic indicating the presence of more than one carrier for any one amino acid. Moreover distinct transport systems for neutral, acidic and basic amino acids were kinetically characterized. Based on competition experiments neutral amino acids were absorbed by all transport systems. Aspartic acid entered the cells via its own carrier and via the basic carrier while arginine was taken up only by the basic carrier. Neutral amino acids such as ʟ-leucine or ʟ-phenylalanine were taken up faster than acidic or basic amino acids.

scholarly journals Substrate specificity of amino acid transport in sheep erythrocytes

1977 ◽  
Vol 162 (1) ◽  
pp. 33-38 ◽  
Author(s):  
J D Young ◽  
J C Ellory
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Acid Transport ◽  
Inhibitory Potency ◽  
Amino Acid Transport System ◽  
Specific Amino Acid ◽  
Sheep Erythrocytes ◽  
Alpha Beta ◽  
Dibasic Amino Acids

The specificity of amino acid transport in normal (high-glutathione) sheep erythrocytes was investigated by studying the interaction of various neutral and dibasic amino acids in both competition and exchange experiments. Apparent Ki values were obtained for amino acids as inhibitors of L-alanine influx. Amino acids previously found to be transported by high-glutathione cells at fast rates (L-cysteine, L-alpha-amino-n-butyrate) were the most effective inhibitors. D-Alanine and D-alpha-amino-n-butyrate were without effect. Of the remaining amino acids studied, only L-norvaline, L-valine, L-norleucine, L-serine and L-2,4-diamino-n-butyrate significantly inhibited L-alanine uptake. L-Alanine efflux from pre-loaded cells was markedly stimulated by extracellular L-alanine. Those amino acids that inhibited L-alanine influx also stimulated L-alanine efflux. In addition, D-alanine, D-alpha-amino-n-biutyrate, L-threonine, L-asparagine, L-alpha, beta-diaminoproprionate, L-ornithine, L-lysine and S-2-aminoethyl-L-cysteine also significantly stimulated L-alanine efflux. L-Lysine uptake was inhibited by L-alanine but not by D-alanine, and the inhibitory potency of L-alanine was not influenced by the replacement of Na+ in the incubation medium with choline. L-Lysine efflux from pre-loaded cells was stimulated by L-alanine but not by D-alanine. It is concluded that these cells possess a highly selective stero-specific amino acid-transport system. Although the optimum substrates are small neutral amino acids, this system also has a significant affinity for dibasic amino acids.

scholarly journals Amino acid transport in normal and glutathione-deficient sheep erythrocytes

1976 ◽  
Vol 154 (1) ◽  
pp. 43-48 ◽  
Author(s):  
J D Young ◽  
J C Ellory ◽  
E M Tucker
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Cell Types ◽  
The Other ◽  
Acid Transport ◽  
Sheep Erythrocytes ◽  
Uptake Rates

1. Uptake rates for 23 amino acids were measured for both normal (high-GSH) and GSH-deficient (low-GSH) erythrocytes from Finnish Landrace sheep. 2. Compared with high-GSH cells, low-GSH cells had a markedly diminished permeability to D-alanine, L-alanine, α-amino-n-butyrate, valine, cysteine, serine, threonine, asparagine, lysine and ornithine. Smaller differences were observed for glycine and proline, whereas uptake of the other amino acids was not significantly different in the two cell types.

Amino Acid Transport in a Water-mould: The Possible Regulatory Roles of Calcium and N6-(Δ2-isopentenyl)adenine

1975 ◽  
Vol 53 (9) ◽  
pp. 975-988 ◽  
Author(s):  
Danny P. Singh ◽  
Hérb. B. LéJohn
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Amino Acid Transport ◽  
Osmotic Shock ◽  
Inhibitory Effect ◽  
Transport Systems ◽  
Acid Transport ◽  
Isopentenyl Adenine ◽  
Energy Dependent ◽  
Water Mould

Transport of amino acids in the water-mould Achlya is an energy-dependent process. Based on competition kinetics and studies involving the influence of pH and temperature on the initial transport rates, it was concluded that the 20 amino acids (L-isomers) commonly found in proteins were transported by more than one, possibly nine, uptake systems. This is similar to the pattern elucidated for some bacteria but unlike those uncovered for all fungi studied to date. The nine different transport systems elucidated are: (i) methionine, (ii) cysteine, (iii) proline, (iv) serine–threonine, (v) aspartic and glutamic acids, (vi) glutamine and asparagine, (vii) glycine and alanine, (viii) histidine, lysine, and arginine, and (ix) phenylalanine–tyrosine–tryptophan and leucine–isoleucine–valine as two overlapping groups. Transport of all of these amino acids was inhibited by azide, cyanide, and its derivatives and 2,4-dinitrophenol. These agents normally interfere with metabolism at the level of the electron transport chain and oxidative phosphorylation. Osmotic shock treatment of the cells released, into the shock fluid, a glycopeptide that binds calcium as well as tryptophan but no other amino acid. The shocked cells are incapable of concentrating amino acids, but remain viable and reacquire this capacity when the glycopeptide is resynthesized.Calcium played more than a secondary role in the transport of the amino acids. When bound to the membrane-localized glycopeptide, it permits concentrative transport to take place. However, excess calcium can inhibit transport which can be overcome by chelating with citrate. Calculations show that the concentration of free citrate is most important. At low citrate concentrations (less than 1 mM) in the absence of exogenously supplied calcium, enhancement of amino acid transport occurs. At high concentrations (greater than 5 mM), citrate inhibits but this effect can be reversed by titrating with calcium. Evidently, the glycopeptide acts as a calcium sink to regulate the concentration of calcium made available to the cell for its membrane activities.N6-(Δ2-isopentenyl) adenine (a plant growth 'hormone') and analogues mimic the inhibitory effect of citrate and bind to the glycopeptide as well. Replot data for citrate and N6-(Δ2-isopentyl) adenine inhibition indicate that both agents have no more than one binding constant. These results implicate calcium, glycopeptide, and energy-dependent transport of solutes in some, as yet undefinable, way.

Placental amino acid transport

1995 ◽  
Vol 268 (6) ◽  
pp. C1321-C1331 ◽  
Author(s):  
A. J. Moe
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Human Placenta ◽  
Amino Acid Transport ◽  
Single Layer ◽  
Maternal Blood ◽  
Transport Systems ◽  
Amino Acid Transporters ◽  
Acid Transport ◽  
Principal Mechanism

Normal fetal growth and development depend on a continuous supply of amino acids from the mother to the fetus. The placenta is responsible for the transfer of amino acids between the two circulations. The human placenta is hemomonochorial, meaning that the maternal and fetal circulations are separated by a single layer of polarized epithelium called the syncytiotrophoblast, which is in direct contact with maternal blood. Transport proteins located in the microvillous and basal membranes of the syncytiotrophoblast are the principal mechanism for transfer from maternal blood to fetal blood. Knowledge of the function and regulation of syncytiotrophoblast amino acid transporters is of great importance in understanding the mechanism of placental transport and potentially improving fetal and newborn outcomes. The development of methods for the isolation of microvillous and basal membrane vesicles from human placenta over the past two decades has contributed greatly to this understanding. Now a primary cultured trophoblast model is available to study amino acid transport and regulation as the cells differentiate. The types of amino acid transporters and their distribution between the syncytiotrophoblast microvillous and basal membranes are somewhat unique compared with other polarized epithelia. These differences may reflect the unusual circumstance of this epithelium that is exposed to blood on both sides. The current state of knowledge as to the types of transport systems present in syncytiotrophoblast, their regulation, and the effects of maternal consumption of drugs on transport are discussed.

Multiple pathways for cationic amino acid transport in rat thyroid epithelial cell line PC Cl3

2005 ◽  
Vol 288 (2) ◽  
pp. C290-C303 ◽  
Author(s):  
Tiziano Verri ◽  
Cinzia Dimitri ◽  
Sonia Treglia ◽  
Fabio Storelli ◽  
Stefania De Micheli ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Cell Line ◽  
Amino Acid Transport ◽  
Transport Systems ◽  
Residual Fraction ◽  
Acid Transport ◽  
Thyroid Cells ◽  
Cationic Amino Acid ◽  
Rat Thyroid

Information regarding cationic amino acid transport systems in thyroid is limited to Northern blot detection of y+LAT1 mRNA in the mouse. This study investigated cationic amino acid transport in PC cell line clone 3 (PC Cl3 cells), a thyroid follicular cell line derived from a normal Fisher rat retaining many features of normal differentiated follicular thyroid cells. We provide evidence that in PC Cl3 cells plasmalemmal transport of cationic amino acids is Na+ independent and occurs, besides diffusion, with the contribution of high-affinity, carrier-mediated processes. Carrier-mediated transport is via y+, y+L, and b0,+ systems, as assessed by l-arginine uptake and kinetics, inhibition of l-arginine transport by N-ethylmaleimide and neutral amino acids, and l-cystine transport studies. y+L and y+ systems account for the highest transport rate (with y+L > y+) and b0,+ for a residual fraction of the transport. Uptake data correlate to expression of the genes encoding for CAT-1, CAT-2B, 4F2hc, y+LAT1, y+LAT2, rBAT, and b0,+AT, an expression profile that is also shown by the rat thyroid gland. In PC Cl3 cells cationic amino acid uptake is under TSH and/or cAMP control (with transport increasing with increasing TSH concentration), and upregulation of CAT-1, CAT-2B, 4F2hc/y+LAT1, and rBAT/b0,+AT occurs at the mRNA level under TSH stimulation. Our results provide the first description of an expression pattern of cationic amino acid transport systems in thyroid cells. Furthermore, we provide evidence that extracellular l-arginine is a crucial requirement for normal PC Cl3 cell growth and that long-term l-arginine deprivation negatively influences CAT-2B expression, as it correlates to reduction of CAT-2B mRNA levels.

Intestinal Transport of Two Dipeptides Containing the Same Two Neutral Amino Acids in Man

1973 ◽  
Vol 45 (3) ◽  
pp. 291-299 ◽  
Author(s):  
D. B. A. Silk ◽  
D. Perrett ◽  
M. L. Clark
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Transport System ◽  
Amino Acid Transport ◽  
Amino Acid Mixture ◽  
Acid Mixture ◽  
Acid Transport ◽  
Peptide Hydrolysis ◽  
Amino Acid Transport System ◽  
Neutral Amino Acids

1. A double lumen perfusion technique has been used in man to study the absorption of the two neutral amino acids glycine and l-alanine from the two dipeptides, l-alanylglycine and glycyl-l-alanine and from an equivalent amino acid mixture. 2. Glycine was absorbed faster from the dipeptides than from the equivalent amino acid mixture, and the difference in absorption rates of glycine and alanine seen when the equimolar mixture of the amino acids was perfused, was abolished when either dipeptide was perfused. This suggests that dipeptides are taken up by the mucosal cell by a mechanism independent of the amino acid-transport system. 3. The presence of free amino acids in the lumen during perfusion of both dipeptides suggests that hydrolysis occurs at some stage in the uptake process. Intraluminal hydrolysis was insufficient to account for the concentration of the amino acids seen, and their presence is thought to be due to hydrolysis of the dipeptides at the brush border. 4. It is suggested that these results confirm that at least two modes of peptide absorption occur simultaneously, namely, direct peptide uptake, and peptide hydrolysis with subsequent absorption of the released amino acids by the amino acid transport system.

AMINO ACID TRANSPORT IN BRAIN CORTEX SLICES: II. COMPETITION BETWEEN AMINO ACIDS

1962 ◽  
Vol 40 (11) ◽  
pp. 1591-1602 ◽  
Author(s):  
P. N. Abadom ◽  
P. G. Scholefield
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Rat Brain ◽  
Amino Acid Transport ◽  
Brain Cortex ◽  
Transport Systems ◽  
Acid Transport ◽  
Inhibitory Effects ◽  
Brain Cortex Slices ◽  
Cortex Slices

Evidence is presented which indicates that several amino acid transport systems are present in rat brain cortex slices, each with its own specificity with regard to substrate and with regard to amino acids which produce inhibitory effects. The nature of these inhibitory effects may be either direct (competition for a limiting number of sites) or indirect (as they are when glutamate or aspartate cause a decrease in the ATP content).Comparison of the specificities of the glycine transport systems present in rat brain cortex slices and in Ehrlich ascites carcinoma cells indicates that these two systems have little in common and the relation of this finding to the structural requirements necessary for chemotherapeutic activity is discussed.

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