Superficial or Membrane Digestion of Peptides in Dinitrophenol-Inhibited Rat Small Intestine

1979 ◽  
Vol 57 (2) ◽  
pp. 217-220 ◽  
Author(s):  
M. L. G. Gardner
Keyword(s):  
Amino Acids ◽  
Small Intestine ◽  
Free Amino ◽  
Rat Small Intestine ◽  
Peptide Hydrolysis ◽  
Brush Border Enzymes ◽  
Contact Digestion ◽  
Membrane Contact ◽  
Hydrolysis Of ◽  
Important Site

1. Hydrolysis of peptides has been measured in isolated rat small intestine perfused with a pancreatic digest of lactalbumin in the presence of 2,4-dinitrophenol. 2. Although transport of water and amino acids was severely inhibited by 2,4-dinitrophenol, peptide hydrolysis to free amino acids was apparently unimpaired. 3. Only a small fraction of the hydrolysis observed could be accounted for by leakage of enzymes into the lumen. 4. The results show that the brush-border enzymes proximal to the transport mechanism(s) can be an important site of hydrolysis of peptides to amino acids under conditions where the transport of unhydrolysed peptides is inhibited. The results are consistent with the concept of membrane (contact) digestion, although the significance of intracellular hydrolysis and of transmural transport of intact peptides is also discussed.

Mechanisms of Dipeptide Uptake by Rat Small Intestine in Vitro

1971 ◽  
Vol 40 (3) ◽  
pp. 247-259 ◽  
Author(s):  
B. Cheng ◽  
F. Navab ◽  
M. T. Lis ◽  
T. N. Miller ◽  
D. M. Matthews
Keyword(s):  
Amino Acids ◽  
Small Intestine ◽  
Amino Acid ◽  
Acid Uptake ◽  
Rat Small Intestine ◽  
Amino Acid Oxidase ◽  
Wide Range ◽  
Mucosal Cells ◽  
Hydrolysis Of

1. The uptake of l-methionine and glycine as free amino acids, and from their dipeptides by everted rings of rat small intestine in vitro has been investigated. The concentrations used covered a wide range, including values likely to be near those found in the lumen of the intestine. 2. Though no intact peptides were found in the mucosal cells, evidence was obtained which showed that hydrolysis of the peptides was cellular at all concentrations. Total hydrolysis of peptides by the intestine was very great in relation to amino acid uptake over very short incubation times, suggesting that much hydrolysis took place superficially. 3. Except at the lowest concentrations, the rates of uptake of amino acids from the peptides were more rapid than from the equivalent amino acid mixtures. Competition for uptake between glycine and methionine was avoided when they were presented in the form of l-methionylglycine. 4. Anoxia inhibited uptake of methionine from free l-methionine and from l-methionyl-l-methionine. It also inhibited hydrolysis of l-methionyl-l-methionine by intact intestine, but not by intestinal homogenates, suggesting that peptide uptake may be energy-dependent. The l-amino acid oxidase of snake venom, which destroys l-methionine but has no effect on glycine or on the peptides studied, inhibited methionine uptake from peptides when present at high concentrations, suggesting that a major site of hydrolysis is enzyme-accessible. 5. It is suggested that there may be two modes of uptake of amino acids from oligopeptides: (1) surface hydrolysis by mechanisms closely linked to the amino acid entry mechanisms, and (2) peptide entry into the mucosal cells by a special mechanism, followed by intracellular hydrolysis.

Availability of amino acids supplied by constant intravenous infusion of synthetic dipeptides in healthy man

1989 ◽  
Vol 76 (6) ◽  
pp. 643-648 ◽  
Author(s):  
S. Albers ◽  
J. Wernerman ◽  
P. Stehle ◽  
E. Vinnars ◽  
P. Fürst
Keyword(s):  
Amino Acids ◽  
Free Amino Acids ◽  
Free Amino ◽  
Metabolic Clearance ◽  
Amino Acid Solution ◽  
Appreciable Change ◽  
Total Body ◽  
Hydrolysis Of ◽  
Firm Evidence ◽  
Apparently Healthy

1. A commercial amino acid solution supplemented with two synthetic dipeptides, l-alanyl-l-glutamine (Ala-Gln) and glycyl-l-tyrosine (Gly-Tyr), or alternatively with isonitrogenous amounts of free alanine and glycine has been continuously infused over 4 h in six apparently healthy volunteers. 2. The infusion of the solutions was not accompanied by any side effects and the volunteers reported no complaints. 3. Infusion of the alanine- and glycine-supplemented control solution resulted in an increase of the concentration of these amino acids, while no appreciable change in free glutamine concentration was observed and free tyrosine revealed a steady decrease throughout the infusion. 4. Infusion of the peptide-supplemented solution resulted in a prompt equimolar liberation of the constituent free amino acids (glutamine, alanine, tyrosine and glycine), approaching steady state after about 30 min infusion, while only trace but stable concentrations of the two dipeptides were measured throughout the infusion. No peptides were detectable in urine. The findings suggest a nearly quantitative extracellular hydrolysis of the infused dipeptides and indicate a subsequent utilization of the liberated free amino acids. 5. The estimated metabolic clearance rates and total body plasma clearances were very similar for the two dipeptides (Ala-Gln 35.9 ± 9.5 ml min−1 kg−1 and 2.9 ± 0.9 1/min, respectively; Gly-Tyr 33.7 ± 9.5 ml min−1 kg−1 and 2.7 ± 0.9 1/min, respectively); thus there is little difference in the metabolic handling of these dipeptides. 6. The study provides firm evidence that the synthetic dipeptides Ala-Gln and Gly-Tyr are quantitatively hydrolysed and that these peptides can be used as a safe and efficient source of free glutamine and tyrosine as part of a commercial solution.

scholarly journals Isolation of Free Amino Acids via Enzymatic Hydrolysis of Tobacco-Derived F1 Protein

2018 ◽  
Vol 28 (4) ◽  
pp. 179-190
Author(s):  
Mehdi Ashraf-Khorassani ◽  
William M. Coleman ◽  
Michael F. Dube ◽  
Larry T. Taylor
Keyword(s):  
Amino Acids ◽  
Enzymatic Hydrolysis ◽  
Free Amino Acids ◽  
Free Amino ◽  
Protein Concentration ◽  
Enzyme Concentration ◽  
Enzymatic Conversion ◽  
Reaction Conditions ◽  
Analytical Methodology ◽  
Hydrolysis Of

SummaryFree amino acids have been isolated via optimized enzymatic hydrolysis of F1 tobacco protein using two cationic resins (Amberlite IR120 and Dowex MAC-2). Optimized enzymatic conversions of the protein as a result of systematic variations in conditions (e.g., time, temperature, pH, enzyme type, enzyme concentration, anaerobic/aerobic environments, and protein concentration) employing commercially available enzymes, were consistently higher than 50% with qualitative amino acid arrays that were consistent with the known composition of tobacco F1 protein. Amberlite IR120 was shown to have a much higher efficiency and capacity for isolation of amino acids from standard solutions and from hydrolysate when compared with the results using Dowex MAC-2. Two columns packed with conditioned Amberlite IR120 (120 × 10 mm,12–15 g resin) and (200 × 25.4 mm, 60–65 g resin) were used to isolate two batches (2.5–3.0 mg and 13–15 mg) of free amino acids, respectively. A relatively inexpensive analytical methodology was developed for rapid analysis of the free amino acids contained within the enzyme hydrolysate. Commercially available enzymes, when employed in optimized reaction conditions, are very effective for enzymatic conversion of tobacco F1 protein to free amino acids.

scholarly journals Quantitative intestinal digestion of nitrogen in sheep given formaldehyde-treated and untreated casein supplements

1972 ◽  
Vol 27 (1) ◽  
pp. 39-50 ◽  
Author(s):  
J. C. Macrae ◽  
M. J. Ulyatt ◽  
P. D. Pearce ◽  
Jane Hendtlass
Keyword(s):  
Amino Acids ◽  
Organic Matter ◽  
Small Intestine ◽  
Free Amino Acids ◽  
Free Amino ◽  
Dry Matter ◽  
Total N ◽  
Once Daily ◽  
Intestinal Digestion ◽  
Gross Energy

1. In two experiments, sheep prepared with a rumen cannula and with re-entrant cannulas in the duodenum and ileum were continuously fed on diets of dried grass, dried grass plus formalin-treated casein, or dried grass plus untreated casein. Paper impregnated with chromic oxide was given once daily via the rumen fistula.2. In ten 24 h collections of digesta entering the duodenum and eleven 24 h collections of digesta reaching the ileum of sheep given dried grass, there were highly significant correlations between the 24 h flows of Cr marker and the corresponding flows of dry matter, organic matter, nitrogen, gross energy, hemicellulose and cellulose (P < 0.01) at both sites.3. Daily amounts of non-ammonia N and of individual amino acids entering and leaving the small intestine and of total N excreted in faeces and urine are given.4. Net retention of supplementary N was 36% when the supplement was administered as formalin-treated casein, but only 17% when it was administered as untreated casein.5. Formalin treatment of casein significantly increased the daily amounts of non-ammonia N entering the small intestine (P < 0.01) and the amounts of non-ammonia N apparently absorbed therein (P < 0.05).6. Apparent absorption of amino acids from the small intestine was significantly greater (P < 0.05) with treated casein than with untreated casein. There were relative increases in the small amounts of several free amino acids measured, including taurine, in the ileal digesta of sheep receiving the treated casein supplement.

scholarly journals The Effect of Fermentation with Kefir Grains on the Physicochemical and Antioxidant Properties of Beverages from Blue Lupin (Lupinus angustifolius L.) Seeds

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 5791
Author(s):  
Łukasz Łopusiewicz ◽  
Emilia Drozłowska ◽  
Paulina Trocer ◽  
Paweł Kwiatkowski ◽  
Artur Bartkowiak ◽  
...  
Keyword(s):  
Amino Acids ◽  
Free Amino Acids ◽  
Free Amino ◽  
Microbial Population ◽  
Antioxidant Properties ◽  
Lupinus Angustifolius ◽  
Kefir Grains ◽  
Antioxidant Properties Of Beverages ◽  
Hydrolysis Of ◽  
Free Radicals Scavenging

Plant derived fermented beverages have recently gained consumers’ interest, particularly due to their intrinsic functional properties and presence of beneficial microorganisms. Three variants containing 5%, 10%, and 15% (w/w) of sweet blue lupin (Lupinus angustifolius L. cv. “Boregine”) seeds were inoculated with kefir grains and incubated at 25 °C for 24 h. After processing, beverages were stored in refrigerated conditions (6 °C) for 21 days. Changes in microbial population, pH, bioactive compounds (polyphenolics, flavonoids, ascorbic acid), reducing sugars, and free amino acids were estimated. Additionally, viscosity, firmness, color, and free radicals scavenging properties were determined. Results showed that lactic acid bacteria as well as yeast were capable of growing well in the lupin matrix without any supplementation. During the process of refrigeration, the viability of the microorganisms was over the recommended minimum level for kefir products. Hydrolysis of polysaccharides as well as increase of free amino acids was observed. As a result of fermentation, the beverages showed excellent DPPH, ABTS+·, ·OH, and O2− radicals scavenging activities with a potential when considering diseases associated with oxidative stress. This beverages could be used as a new, non-dairy vehicle for beneficial microflora consumption, especially by vegans and lactose-intolerant consumers.

Effects of constituent amino acids on tubular handling of microinfused angiotensin II

1978 ◽  
Vol 234 (4) ◽  
pp. F325-F331 ◽  
Author(s):  
T. N. Pullman ◽  
F. A. Carone ◽  
S. Oparil ◽  
S. Nakamura
Keyword(s):  
Amino Acids ◽  
Angiotensin Ii ◽  
Aspartic Acid ◽  
Free Amino ◽  
Renal Tubules ◽  
Urinary Recovery ◽  
Proximal Tubular ◽  
Distal Tubules ◽  
Proximal Convolution ◽  
Hydrolysis Of

[14C]angiotensin II ([14C]AII) was microinjected alone or with excess L-isoleucine (IIe) or L-aspartic acid (Asp) into renal tubules of anesthetized rats. Urinary excretion of 14C-labeled material was measured, and the intact peptide and its metabolites were identified and quantified. When isoleucine was administered with [14C]AII, urinary recovery of the 14C-labeled material increased directly with distance of infusion site from glomerulus, and most of the radioactivity in urine was [14C]Ile. The data suggest that isoleucine interfered with reabsorption of [14C]Ile derived from hydrolysis of [14C]AII and less so with the hydrolysis itself. When aspartic acid was administered with [14C]AII into the proximal 5/6 of the proximal convolution, total urinary recovery of the 14C-labeled material was unchanged, but percentage of recovery as [14C]AII increased; with infusion into the distal 1/6 of the proximal convolution, total urinary recovery of the 14C labele increased. The data suggest that aspartic acid interfered with the enzymatic hydrolysis of [14C]AII and reabsorption of isoleucine. In distal tubules the 14C label was almost completely recovered as intact [14C]AII in all protocols. The results show that free amino acids influence proximal tubular handling of small linear peptides in rats.

Dietary regulation of intestinal transport of the dipeptide carnosine

1988 ◽  
Vol 255 (2) ◽  
pp. G143-G150 ◽  
Author(s):  
R. P. Ferraris ◽  
J. Diamond ◽  
W. W. Kwan
Keyword(s):  
Amino Acids ◽  
Cell Surface ◽  
Dietary Protein ◽  
Free Amino Acids ◽  
Free Amino ◽  
Intestinal Transport ◽  
Dietary Regulation ◽  
Dietary Protein Level ◽  
Low Protein ◽  
Hydrolysis Of

Uptake of the dipeptide L-carnosine was measured in everted intestinal sleeves of mice whose dietary protein level or else proportion of protein in the form of free amino acids was varied experimentally. Carnosine uptake was highest in the jejunum, regardless of ration. Compared with a low-protein (18%) ration, a high-protein (72%) ration stimulated carnosine uptake by 30-70% in duodenum and jejunum (but not in ileum). This stimulation was observed even in the presence of peptidase inhibitors that inhibit cell surface hydrolysis of dipeptides. Measured carnosine hydrolysis was low or negligible. Carnosine uptake was the same in mice fed 54% unhydrolyzed casein, 54% partly hydrolyzed casein, and 54% free amino acids formulated so as to stimulate a complete hydrolysate of casein. Thus carnosine uptake is regulated by dietary levels of amino acids, peptides, and proteins, all of which seem equally effective at inducing carnosine transporters.

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