Enzymatic influences on amino acid transport across the small intestine (original) (raw)
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Abbreviations used in this paper: AIB, 2-aminoisobutyric acid; GGT, y-glutamyltranspeptidase; MeAIB, 2-(methylamino) isobutyric acid; NAA, neutral amino acid; NBAT, neutral and basic amino acid transporter; ORT, oral rehydration therapy; rBAT, related to b °'+ amino acid transporter; SGLT, sodium-dependent glucose transporter; Vm~x, maximum velocity.
The uptake of amino acids by the intestine
Biochimica et biophysica acta, 1954
It has been shown by WISEMAN 1 and AGAR, HIRD AND SIDHU 2 that isolated loops of rat's intestine transfer L-but not D-amino acids against a concentration gradient. These workers therefore suggested that the process of transfer was an active one. The discovery that cyanide and dinitrophenol interfered with this process (AGAR et al. ~)
Amino Acid Transport Across Mammalian Intestinal and Renal Epithelia
Physiological Reviews, 2008
The transport of amino acids in kidney and intestine is critical for the supply of amino acids to all tissues and the homeostasis of plasma amino acid levels. This is illustrated by a number of inherited disorders affecting amino acid transport in epithelial cells, such as cystinuria, lysinuric protein intolerance, Hartnup disorder, iminoglycinuria, dicarboxylic aminoaciduria, and some other less well-described disturbances of amino acid transport. The identification of most epithelial amino acid transporters over the past 15 years allows the definition of these disorders at the molecular level and provides a clear picture of the functional cooperation between transporters in the apical and basolateral membranes of mammalian epithelial cells. Transport of amino acids across the apical membrane not only makes use of sodium-dependent symporters, but also uses the proton-motive force and the gradient of other amino acids to efficiently absorb amino acids from the lumen. In the basolate...
The Journal of nutrition, 2002
The present study examined the functional characteristics of the inward [(14)C]-L-leucine transporter in two intestinal epithelial cell lines (human Caco-2 and rat IEC-6). The uptake of [(14)C]-L-leucine was largely promoted through an energy-dependent and sodium-insensitive transporter, although a minor component of [(14)C]-L-leucine uptake ( approximately 15%) required extracellular sodium. [(14)C] -L-leucine uptake was insensitive to N-(methylamino)-isobutyric acid, but competitively inhibited by 2-aminobicyclo(2,2,1)-heptane-2-carboxylic acid (BCH). Both L- and D-neutral amino acids, but not acidic and basic amino acids, markedly inhibited [(14)C]-L-leucine accumulation. The efflux of [(14)C]-L-leucine was markedly increased (P < 0.05) by L-leucine and BCH, but not by L-arginine. In IEC-6 cells, but not in Caco-2 cells, the uptake of [(14)C]-L-leucine at acidic pH (5.0 and 5.4) was greater (P < 0.05) than at pH 7.4. In conclusion, it is likely that system B(0) might be res...
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1993
High-and low-affinity Na+-dependent neutral L-a-amino acid transporters were solubilized with 0.25% octaethylene glycol dodecyl ether (C12E8) after removal of the proteins from the brush-border membrane vesicles with 2% CHAPS and 4 M urea. When the CHAPS-insoluble protein was treated with papain before its solubilization with C12E8, a substantial amount of protein was removed without any decrease of the transport activities. The solubilized transporters were reconstituted into proteoliposomes after removal of C12E a with Bio-Beads SM2. Several parameters proved to be important for optimal reconstitution efficiency: (a) the type of detergent, and (b) the phospholipid/protein and detergent/protein ratio during reconstitution, and (c) the salt concentration during reconstitution. Reconstituted proteoliposomes showed rapid uptake of neutral L-a-amino acids but not imino acid, basic or acidic amino acids driven by an electrochemical potential of Na ÷ (out > in). The uptakes under low-and high-substrate condition were further augmented by an artificial membrane potential introduced by K ÷ diffusion via valinomycin (negative interior). Kinetic analysis revealed that both the brush-border membranes and the solubilized fraction involved two carrier-mediated pathways for alanine transport. The kinetic parameters were determined by curve fitting with a computer to be Ka-0.28 mM (0.21 mM) and Kt2 = 43.2 mM (28.4 mM), respectively (those with brush-border membrane vesicles in parentheses). Studies on the specific activities for transport of individual amino acids under low or high substrate concentration and the cross-inhibitory effects of various amino acids on alanine uptake (low concentration) revealed that these transporters possess broad specificity for neutral L-a-amino acids.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1990
We have characterized the transcellular transport of a large neutral amino acid (LNAA) in Caco-2 cell monolayers. The apical (AP) to basolateral (BL) transport of phenylalanine (Phe) was approximately 10-times faster than BL-to-AP transport. The evidence for the carrier-mediated AP-to-BL transport of Pbe include: (a) temperature dependence and saturability, (b) Phe transport was not affected by a reverse gradient, (c) the activation energy for transport was 12.0 kcal/tool, and (d) an excess amount of unlabeled Phe caused a 75% reduction in transport rate and a delay (lag time) in the appearance of Phe in the BL side. The V m and K m for Phe transport were 572.4 pmol • mg protein-t. min-t and 0.56 raM, respectively. Phe transport was decreased in the absence of glucose and in the presence of sodium azide or ouahain. The carrier interacted with LNAAs and with cationic amino acids but not with small neutral or anionic amino acids.
The Histochemical journal, 1999
Peptide transporter-1 is a H+/peptide cotransporter responsible for the uptake of small peptides and peptide-like drugs, and is present in the absorptive epithelial cells of the villi in the small intestine (duodenum, jejunum, and ileum). It has been localized to the apical microvillous plasma membrane of the absorptive epithelial cells of the rat small intestine using the immunogold electron microscopic technique. Digital image analysis of the jejunum revealed that the transporter protein was abundant at the tip of the villus and that the amount decreased from the tip of the villus to its base. The effect of dietary administration of amino acids and starvation on the expression of PepT1 in the jejunum was examined by immunoblotting and image analysis of immunofluorescence. Starvation markedly increased the amount of peptide transporter present, whereas dietary administration of amino acids reduced it. The gradient of the transporter protein along the crypt-villus axis was maintaine...
Absorption and Transportation of Amino acids in animals : A Review
2017
Small peptides (primarily di-and tri-peptides) and amino acids are absorbed from the small intestine. Ileum and jejunum are the more active sites of amino acid absorption. Both peptide and amino acids can be absorbed against a concentration gradient and require energy in the form of ATP. The energy dependent transport of amino acids is linked with co-transport of Na + , while in case of peptides it is linked with co-transport of protons (H +). Animal's needs of the for body growth and maintenance is fulfilled by free amino acids and peptides. Although both are absorbed from the gastrointestinal tract, however, absoprtion of peptides occurs at much rate as compared to free amino acids. In ruminants peptides are more important form of amino acid than free amino acids, and major sites of peptide absorption includes rumen and omasum. Ruminal microorganisms potentially are vital in regulating the composition of peptides offered for absorption. These observations will have major effect on understanding the processes of digestion and absorption of proteins in ruminants. Furthermore, these observations will dramatically alter many strategies used in providing for the proper protein nutrition of ruminants.
The role of sodium ion in the transport of amino acids by the intestine
Biochimica et biophysica acta, 1965
I. Decreasing the incubation medium Na+ concentration below physiologic levels resulted in decreased transport of Na + and water in the isolated rabbit jejunum as well as diminution of amino acid transport. 2. Ouabain inhibited the transport of Na+ and amino acids in everted jejunal sacs. 3. Reduction of medium Na+ was associated with decreased tissue Na + and K+ content while ouabain produced elevated tissue Na+ and reduced tissue K+ concentrations. 4. Kinetic analysis of amino acid-uptake data showed that ouabain and reduction of medium Na + caused a slowing of both influx and, to a lesser degree, effiux coefficients. 5. The Na+ ion was shown to affect energy-independent (diffusion) as well as energy-dependent (active) transport of amino acids.