Brush-border amino acid transport mechanisms in carnivorous eel intestine

1989 ◽  
Vol 257 (3) ◽  
pp. R506-R510 ◽  
Author(s):  
C. Storelli ◽  
S. Vilella ◽  
M. P. Romano ◽  
M. Maffia ◽  
G. Cassano
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Brush Border ◽  
Amino Acid Transport ◽  
Membrane Vesicles ◽  
Anguilla Anguilla ◽  
Neutral Amino Acid ◽  
Transport Systems ◽  
European Eel ◽  
Acid Transport

Brush-border membrane vesicles (BBMV) were prepared from European eel (Anguilla anguilla) intestinal epithelium by a magnesium-ethylene glycolbis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) precipitation technique. Amino acid transport by these purified vesicle preparations was investigated using either radiolabeled substrates or the voltage-sensitive fluorescent dye 3,3'-diethylthiadicarbocyanine iodide [DiSC2(5)]. All amino acids tested exhibited carrier-mediated, Na+-dependent and Na+-independent transfer processes plus diffusion. The only exceptions were glutamic acid and proline, which displayed Na+ dependency and diffusion but did not appear to be transported by Na+-independent agencies. Carrier-mediated transport kinetic constants (Kapp and Jmax) for several amino acids are reported. Cis-inhibition experiments suggested the presence of at least four distinct Na+-dependent transport systems in eel intestinal BBMV: 1) an anionic transport process for glutamic and aspartic acids; 2) a cationic mechanism for lysine and arginine; 3) a relatively specific neutral amino acid carrier for proline and alpha-(methylamino)isobutyric acid; and 4) a nonspecific neutral amino acid system for most other substrates of this group. This scheme for carnivorous fish intestine most closely approximates that reported for mammalian gut with minor dissimilarities that may relate to metabolic differences or specific dietary requirements of the two vertebrate groups.

AMINO ACID TRANSPORT SYSTEMS IN BRUSH-BORDER MEMBRANE VESICLES FROM LEPIDOPTERAN ENTEROCYTES

1989 ◽  
Vol 143 (1) ◽  
pp. 87-100
Author(s):  
GIORGIO M. HANOZET ◽  
BARBARA GIORDANA ◽  
V. FRANCA SACCHI ◽  
PAOLO PARENTI
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Glutamic Acid ◽  
Brush Border ◽  
Amino Acid Transport ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Transport Systems ◽  
Acid Transport ◽  
Luminal Membrane

The presence of different potassium-dependent amino acid transport systems in the luminal membrane of the larval midgut of Philosamia cynthia Drury (Saturnidae, Lepidoptera) was investigated by means of countertransport experiments performed with brush-border membrane vesicles. The vesicles were preloaded with 14 different unlabelled amino acids, whose ability to elicit an intravesicular accumulation over the equilibrium value of six labelled amino acids (L-alanine, L-leucine, L-phenylalanine, L-glutamic acid, L-lysine and L-histidine) was tested. For histidine, the results were compared with those obtained from inhibition experiments, in which the same 14 amino acids were used as inhibitors on the cis side of the brush-border membrane. The data demonstrate the presence in the lepidopteran luminal membrane of distinct transport pathways for lysine and glutamic acid. The transport of most neutral amino acids, with the exclusionof glycine and proline, seems to occur through a system that may be similar to the neutral brush-border system (NBB) found in mammalian intestinal membranes. This system is also able to handle histidine.

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 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.

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