Intestinal absorption of amino acids and peptides

Matthews, D. M.

doi:10.1079/pns19720033

Cited by 36 publications

(17 citation statements)

References 38 publications

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“…It is of special interest that Lys, Glu and Asp, which are absorbed more slowly from amino acid mixtures than any other amino acids (Adibi e l al., 1967) are taken up from several dipeptides more rapidly than from the equivalent mixtures of free amino acids. This provides further evidence that experiments using amino acid mixtures do not give a true picture of the intestinal transport of protein digestion products (Matthews, 1972b). The results have a bearing on the suggestion that acidic amino acids are largely absorbed as peptides whereas basic amino acids are absorbed in the free form (Gray & Cooper, 1971).…”

Section: Discussionmentioning

confidence: 87%

Uptake of Dipeptides Containing Basic and Acidic Amino Acids by Rat Small Intestine in Vitro

Burston¹,

Addison²,

Matthews³

1972

Clinical Science

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1. The characteristics of transport and hydrolysis of twenty-two dipeptides containing basic and acidic amino acids by rat ileal rings were investigated in vitro. The peptides included combinations of basic and neutral, basic and basic, basic and acidic, acidic and acidic, and acidic and neutral amino acids.2. All peptides studied were removed intact from the bulk phase of the incubation medium, though, in general, only free amino acids appeared in the tissue. Uptake of one or both constituent amino acids was greater from the peptide than from the equivalent amino acid or amino acid mixture in the case of at least one peptide from each group and in eighteen of the twenty-two peptides studied. In general, there was no relationship between the extent of uptake of amino acids from peptides and the extent of their hydrolysis by the system. The results support the hypothesis that there is more than one mode of uptake of amino acids from peptides.3. Hydrolysis of y-glutamyl-L-glutamic acid by intact intestine or intestinal homogenate was slight, and intact peptide was taken up by the tissue. Uptake of free glutamic acid from this peptide was poor. Comparison of y-glutamyl-L-glutamic acid with three other slowly hydrolysed dipeptides, glycyl-D-valine, sarcosylglycine and glycylsarcosine, suggested that all four were transported into the mucosal cells and hydrolysed intracellularly. The results indicate that the presence of a y-linkage or a D-amino acid, or methylation of the free amino group as in sarcosylglycine, impair both transport and hydrolysis of peptide, but that attachment of a methyl group to the N of the peptide bond, as in glycylsarcosine, impairs hydrolysis but has no effect on peptide transport. 4. L-Aspartic acid and L-glutamic acid were extensively transaminated by the intestine, whether presented as free amino acids or in peptides. Evidence was obtained suggesting that production of alanine from aspartic acid resulted from direct transamination of aspartic acid with pyruvic acid, rather than from a sequence of two reactions involving aspartate and alanine aminotransferases.

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Section: Discussionmentioning

confidence: 87%

Uptake of Dipeptides Containing Basic and Acidic Amino Acids by Rat Small Intestine in Vitro

Burston¹,

Addison²,

Matthews³

1972

Clinical Science

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“…In addition, paracellular uptake could contribute to Na ϩ -independent uptake of neutral amino acids. Alternatively, neutral amino acids can be absorbed as di-or tripeptides (33). Uptake of the PepT1 substrate carnosine (34) was lower than leucine uptake, suggesting that amino acid uptake via B 0 AT1 has a similar or even higher capacity than peptide uptake via PepT1 (Slc15a1) at a substrate concentration of 100 M. There was no compensatory increase of peptide uptake in Slc6a19 nullizygous mice.…”

Section: Discussionmentioning

confidence: 97%

Impaired Nutrient Signaling and Body Weight Control in a Na+ Neutral Amino Acid Cotransporter (Slc6a19)-deficient Mouse

Bröer

Juelich

Vanslambrouck

et al. 2011

Journal of Biological Chemistry

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Amino acid uptake in the intestine and kidney is mediated by a variety of amino acid transporters. To understand the role of epithelial neutral amino acid uptake in whole body homeostasis, we analyzed mice lacking the apical broad-spectrum neutral (0) amino acid transporter B 0 AT1 (Slc6a19). A general neutral aminoaciduria was observed similar to human Hartnup disorder which is caused by mutations in SLC6A19. Na ؉ -dependent uptake of neutral amino acids into the intestine and renal brushborder membrane vesicles was abolished. No compensatory increase of peptide transport or other neutral amino acid transporters was detected. Mice lacking B 0 AT1 showed a reduced body weight. When adapted to a standard 20% protein diet, B 0 AT1-deficient mice lost body weight rapidly on diets containing 6 or 40% protein. Secretion of insulin in response to food ingestion after fasting was blunted. In the intestine, amino acid signaling to the mammalian target of rapamycin (mTOR) pathway was reduced, whereas the GCN2/ATF4 stress response pathway was activated, indicating amino acid deprivation in epithelial cells. The results demonstrate that epithelial amino acid uptake is essential for optimal growth and body weight regulation.In a typical Western diet humans consume about 80 -100 g of protein per day. Proteins are hydrolyzed by the action of secreted and membrane-bound peptidases into individual amino acids, di-and tripeptides (1). Individual amino acids are taken up by a variety of amino acid transporters, whereas diand tripeptides are absorbed by the peptide transporter PepT1 (SLC15A1) (2). Together this digestive process makes 90 -95% of ingested proteins available to the body. Protein demand is particularly high during growth and development when new proteins are required to build up body mass. In the adult, protein recycling is quite efficient, and only 50 g of protein is needed per day to replace protein lost through urine and feces.The bulk of neutral amino acids is absorbed in the intestine by the neutral amino acid transporter B 0 AT1 (SLC6A19), which is also expressed in the kidney where it mediates reabsorption of neutral amino acids (3). Expression studies in heterologous systems have shown that B 0 AT1 accepts all neutral amino acids with a preference for large neutral amino acids such as branched-chain amino acids and methionine (4, 5). These amino acids are taken up with a K m of about 1 mM, whereas smaller amino acids are taken up with higher K m values. Glycine and proline are poor substrates of B 0 AT1. As a result additional transporters are involved in the uptake of imino acids and glycine, such as PAT1 (SLC36A1), PAT2 (SLC36A2), and IMINO (SLC6A20) (6). Additional transport systems for other neutral amino acids in the kidney and intestine have been proposed; these include a specific intestinal transporter for methionine and phenylalanine (7) and the amino acid antiporter ASCT2 (SLC1A5) as a mediator of small neutral amino acids and glutamine uptake in kidney and intestine (8).Efficient trafficking and sur...

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“…The digestion and absorption of protein is a very complicated process (Porter & Rolls, 1971;Matthews, 1972;Amato, 1973). First there are the sequential effects of a battery of proteases and peptidases secreted into the lumen of the intestinal tract.…”

mentioning

confidence: 99%

Damage to nutritional value of plant proteins by chemical reactions during storage and processing

Synge

1976

Plant Food Hum Nutr

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The nutritive function of proteins for monogastric animals may be simply to supply the body with amino acids. However, the complexities of digestion, absorption and metabolism imply that amino acid composition, determined chemically after hydrolysis, can only be a very rough guide (usually setting upper limits) to the nutritional value of proteins.Chemical reactions which may affect nutritional values of proteins are discussed at length. Chemical tests, for determining the extent to which these reactions have occurred, are increasing, both in number and usefulness. However, to derive practical benefits from chemical tests, frequent paxallel nutritional assessments must be conducted using animals.

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Intestinal absorption of amino acids and peptides

Cited by 36 publications

References 38 publications

Uptake of Dipeptides Containing Basic and Acidic Amino Acids by Rat Small Intestine in Vitro

Uptake of Dipeptides Containing Basic and Acidic Amino Acids by Rat Small Intestine in Vitro

Impaired Nutrient Signaling and Body Weight Control in a Na+ Neutral Amino Acid Cotransporter (Slc6a19)-deficient Mouse

Damage to nutritional value of plant proteins by chemical reactions during storage and processing

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