Digestion of tripeptides and disaccharides: relationship with brush border hydrolases

Arvanitakis, Constantine; Ruhlen, J; Folscroft, John; Rhodes, JB

doi:10.1152/ajplegacy.1976.231.1.87

Cited by 10 publications

(4 citation statements)

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“…Several aminopeptidases exist to reduce polypeptides, but two having broad specificities have been generalized (Danielson and Hansen, 2006). Aminopeptidase A can be credited for hydrolyzing the acidic amino acids, glutamic and aspartic acids as well as the large aliphatic and aromatic ones from the amino end of peptides while aminopeptidase N is credited with preference for the neutral ones (Arvanitakis et al, 1976;Benajiba and Maroux, 1981;Feracci et al, 1981;Matsushima et al, 1991). Such actions seem particularly favorable for release of the aliphatic-aromatic amino acids previously availed at the amino end by pepsin.…”

Section: Conducting Absorptionmentioning

confidence: 99%

Gastric digestion of protein through pancreozyme action optimizes intestinal forms for absorption, mucin formation and villus integrity

Moran

2016

Animal Feed Science and Technology

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a b s t r a c tRecovery of dietary protein proceeds through two phases of digestion before suitable forms exist for absorption. The first phase engages the gastric system where low pH weakens overall structures allowing pepsin to disrupt hydrophobic bonding and enhance aqueous compatibility. Secondly, trypsin, chymotrypsin and elastase proteolysis in conjunction with carboxypeptidases A and B cooperate to form a mixture of free amino acids and peptides that progressively arise in the small intestinal lumen. Free amino acids are dominated by the aromatic, aliphatic and basic ones while resulting peptides largely involve the nonessentials.Motility convectively transfers digestion products to the unstirred water layer of the upper villus where filtration limits entry to low molecular weight solutes that can be further digested by underlying enzymes to optimize membrane absorption. Mucin oligosaccharides are credited for creating a microenvironment having reduced pH's ∼5.5-6.0 that favors enzymes finalizing digestion as well as absorption of two type peptides. This pH is speculated to optimize peptide forms having either a zwitterion-like charge for proton gradient transfer or be non-dissociated and passively diffused. A high frequency of peptides having either glycine or proline can be rationalized as providing particularly favorable electronic terms for peptide absorption by either approach while being non-competitive.The upper villus has first access to absorbed products where goblet cells assure continuance of mucin and continuity of the unstirred water layer. Glutamine is their dominant nutrient for synthesis of mucin oligosaccharides while also providing glutamic acid for either formation of its associated protein or is consumed for energy. Dietary cystine and threonine are frequently limiting, and their assurance is necessary for the mucin core while ready availability of glycine and/or serine together with proline also foster mucin formation. Unused absorbed products descend the villus in venules adjacent to the surface and provide nutrition as well as information about the lumen for adaptation of replacement cells. Sustaining the villus with absorbed nutrients takes priority for continuation of operational efficiency before their entry into the portal system and subsequent body use.

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Section: Conducting Absorptionmentioning

confidence: 99%

Gastric digestion of protein through pancreozyme action optimizes intestinal forms for absorption, mucin formation and villus integrity

Moran

2016

Animal Feed Science and Technology

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“…Das Tripeptid Pro-Gly-Gly hingegen wird kaum durch die membrangebundenen Peptidhydrolasen gespalten, so daO fur dieses naturliche Tripeptid ein intakter Eintritt angenommen wird [33]. Daher ist auch fur diese Peptide ein Transport in intakter Form durch die luminale Plasmamembran der Enterozyten postuliert worden.…”

Section: Die Ahwrption Von Triiind Tetrapeptidenunclassified

Fortschrittsbericht Die intestinale Phase der Peptidabsorption

Friedrich

1982

Nahrung

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Peptides and not amino acids are the prevailing degradation products of protein digestion which are formed in the intestinal lumen and are absorbed from the mucosa. These two families differ in absorption. The differences become manifest when the absorption of peptide mixtures is compared with that of equimolecular mixtures of free amino acids. The absorption of peptides occurs in two different ways: 1. Transport of intact peptides through the membrane into the mucosal cell and subsequent hydrolysis by intracellular peptide hydrolases. 2. Hydrolysis of the peptides by peptide hydrolases localized on the luminal side of the mucosal cell membrane and subsequent transport of the amino acids thus formed through the membrane. The two mechanisms of absorption do not exclude each other. The way by which energy is supplied for the transport is not yet elucidated. The transport of intact peptides is of nutritive importance only in case of dipeptides and tripeptides. It enables in particular the introduction of peptides that cannot be cleft by membrane-bound peptide hydrolases. The hydrolysis of peptides by membrane-bound peptide hydrolases and the subsequent transport of released amino acids is of importance for long-chain peptides. The difference in absorbing behaviour between the free amino acids released in the intestinal lumen and the amino acids released by peptide hydrolases at the mucosal membrane is discussed.

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“…Rubino et al (16), using mucosal strips in influx chambers, characterized an energy-dependent transport apparatus for peptides which could be competitively inhibited by dipeptides buit not by free amino acids. The extensive work of Matthews in animals (18) and Adibi in man (7) showed a marked advantage for amino acid absorption from small peptides over an equivalent mixture of the free amino acids and recent thorough studies of mutual inhibition between dipeptides (19) (20) and man (7) has suggested that peptides suich as Leti-Leti-Leu and LeuiGly-Gly may be hydrolyzed to a great extent before absorption since higlh concentrations of free leuicine appear in intestinal fluid simultaneously with the disappearance of the test peptide. This intraluminal accumulation of leucine couild be markedly enhanced by perfuision of isoletucine along with the leuicinecontaining tripeptide (7) stuggesting that the leucine is released at a site where it must compete withl isoleucine for the netutral amino acid transport mechanism.…”

Section: In Vivo Intestinal Perfusion Experimentsmentioning

confidence: 99%

“…In these experiments, the tetrapeptide disappeared rapidly from the test solution (20 ,umol/s per cm2 in vitro; 17 ,tmol/s per cm2 in vivo) by sequential removal of amino acid residues from the N-terminus to yield amino acids and the C-terminal dipeptide. In gut sac experiments, 61-100% of these products of hydrolysis appeared in the incubation medium and the remainder in the tissue.…”

mentioning

confidence: 95%