Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “dipeptides”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 685 records · Page 38Linked to original sources
PubMed1980

Age-dependent change in intestinal absorption of dipeptides and their constituent amino acids in the guinea pig.

The influxes from the mucosal solution to the enterocytes were investigated for glycylglycine, glycyl-L-leucine, and their constituent amino acids in isolated intestinal segments from suckling (3 to 4 days), weanling (10 to 14 days), and adult guinea pigs. Glycine and L-leucine influxes from the mucosal solution containing free glycine or L-leucine were not significantly different between sucklings and adults in either the jejunum or the ileum. On the other hand, glycylglycine and glycyl-L-leucine influxes were significantly greater in the following sequence: sucklings > weanlings > adults. Such age-dependent difference in dipeptide influx was more prominent in the jejunum than in the ileum. Kinetically, such developmental change in dipeptide influx was found to be related to the change in the value of Jmax (the maximum influx). The data indicated that the intact-peptide transfer mechanism has more important significance in protein hydrolysate absorption in immature stages of animals than in adults.

Aging↗
PubMed1987

Development of dipeptide transport in rat renal brush border membranes: studies with glycylsarcosine.

Dipeptide-proton cotransport was studied in rat renal brush border membrane vesicles from animals of different ages, starting at 7 days after birth. In the presence of an inward-directed proton gradient, glycyl-sarcosine uptake exhibited the overshoot phenomenon in all age groups studied. The magnitude of the "overshoot" increased with age and maximum accumulation of glycyl-sarcosine was observed in 42-day-old rat renal brush border membrane vesicles. Kinetic studies with glycyl-sarcosine indicated changes only in maximal velocity without any significant change in the apparent affinity value during the postnatal development of the renal brush border membrane. Since the Na+-H+ exchanger located at the brush border membrane is primarily responsible for the generation of the proton gradient, the driving force for dipeptide transport, we also measured the Na+-H+ exchanger activity in rat renal brush border membrane vesicles from suckling and adult animals. The exchanger activity was significantly greater in the adult rats compared to the suckling rats. In addition, we have confirmed in the present study previous findings from other laboratories that the activities of the Na+ gradient-driven glucose and amino acid transport systems in renal brush border membrane vesicles were higher in the adult than in the suckling rats.

Age Factors↗
PubMed1999

Tracheal barrier and the permeability of hydrophilic drugs and dipeptides.

The permeability of model hydrophilic compounds with different molecular weights and model dipeptides were examined to characterize the tracheal epithelial barrier in in vitro experiments using excised rabbit trachea. 6-Carboxyfluorescein (6-CF; 376 Da) and fluorescein isothiocyanate (FITC)-dextrans (FDs) with varying molecular weights (4 to 70 kDa) were used as model hydrophilic and macromolecular compounds, and glycyl-D-phenylalanine (Gly-D-Phe) and glycyl-L-phenylalanine (Gly-L-Phe) were used as model dipeptides in this experiment. The apparent permeability coefficients (Papp) of 6-CF and FDs with Mw 376 Da to 70 kDa ranged from 2.35x10(-7) to 4.05x10(-10)cm/s and exhibited a good inverse correlation with their molecular weights. The tracheal permeability of 6-CF, FD-4 (4 kDa) and FD-10 (10 kDa) were increased over three fold by 10 mM glycocholate, which is an absorption enhancer. The Papp of Gly-D-Phe was 1.03x10(-6)cm/s and there was no metabolism during tracheal permeation. Gly-L-Phe was immediately degraded in the mucosal fluid and its intact form was not detected in serosal fluid during the 150 min experimental period. These results suggest that absorption of some peptide drugs via the respiratory tract may contribute to their systemic delivery following pulmonary administration by intratracheal insufflation and instillation.

Animals↗
PubMed2005

D-Amino acid dipeptide production utilizing D-alanine-D-alanine ligases with novel substrate specificity.

D-Alanine-D-alanine ligase (Ddl) is an important enzyme in the synthesis of bacterial peptidoglycan. The genes encoding Ddls from Escherichia coli K12 (EcDdlB), Oceanobacillus iheyensis JCM 11309 (OiDdl), Synechocystis sp. PCC 6803 (SsDdl) and Thermotoga maritima ATCC 43589 (TmDdl), the genomic DNA sequences of which have been determined, were cloned and the substrate specificities of these recombinant Ddls were investigated. Although OiDdl had a high substrate specificity for D-alanine; EcDdlB, SsDdl and TmDdl showed broad substrate specificities for D-serine, D-threonine, D-cysteine and glycine, in addition to D-alanine. Four D-amino acid dipeptides were produced using EcDdlB, and D-amino acid homo-dipeptides were successfully produced at high yields except for D-threonyl-D-threonine.

Amino Acid Sequence↗
PubMed1997

Photolysis (193 nm) of aliphatic dipeptides in aqueous solution.

The photodecomposition of four aliphatic dipeptides containing valine and methionine was studied in neutral solution upon excitation at 193nm. The quantum yields of ionization and decomposition in Ar-saturated aqueous solution are phi(e)- = 0.06-0.16 and phi(d) = 0.06-0.16, respectively. Phi(d) is enhanced (0.08-0.28) under N2O, where the hydrated electrons are converted into OH radicals. A comparison of the phi(d) values of dipeptides with those of monomeric amino acids indicates efficient decomposition of the peptide bond (bond scission).

Dipeptides↗
PubMed2005

Potentials of mean force for the interaction of blocked alanine dipeptide molecules in water and gas phase from MD simulations.

We calculate potentials of mean force (PMFs) for the intermolecular interaction of two blocked alanine dipeptide (AcAlaNHMe) molecules in water and gas phase at two temperatures, 278 and 300 K, from all-atom molecular dynamics simulations. Simple models based on buried solvent accessible surface and one-dimensional potentials derived from distance-based radial distribution functions are not capable of expressing the short- and long-range complexity of the solute-solute interactions in water. Instead, radial and angular variations in the PMFs are observed with the two-dimensional potentials. The strength of the interactions for specific relative orientations of the molecules in the two-dimensional PMFs is more than double that observed in the one-dimensional PMFs. The populations of specific blocked alanine dipeptide conformations in water, such as alpha(R) and PPII, vary with temperature, and most significantly, with the distance between the centers of mass. A preference for helical conformations is observed at close encounter between molecules.

Alanine↗
PubMed2006

Ile-phe dipeptide self-assembly: clues to amyloid formation.

Peptidic self-assembled nanostructures are said to have a wide range of applications in nanotechnology, yet the mechanistic details of hierarchical self-assembly are still poorly understood. The Phe-Phe recognition motif of the Alzheimer's Abeta peptide is the smallest peptide able to assemble into higher-order structures. Here, we show that the Ile-Phe dipeptide analog is also able to self-associate in aqueous solution as a transparent, thermoreversible gel formed by a network of fibrillar nanostructures that exhibit strong birefringence upon Congo red binding. Besides, a second dipeptide Val-Phe, differing only in a methyl group from the former, is unable to self-assemble. The detailed analysis of the differential polymeric behavior of these closely related molecules provides insight into the forces triggering the first steps in self-assembly processes such as amyloid formation.

Amyloid↗
PubMedDate not supplied

Rose Bengal-sensitized photooxidation of the dipeptides L-tryptophyl-L-phenylalanine, L-tryptophyl-L-tyrosine and L-tryptophyl-L-tryptophan: kinetics, mechanism and photoproducts.

The Rose Bengal-sensitized photooxidations of the dipeptides l-tryptophyl-l-phenylalanine (Trp-Phe), l-tryptophyl-l-tyrosine (Trp-Tyr) and l-tryptophyl-l-tryptophan (Trp-Trp) have been studied in pH 7 water solution using static photolysis and time-resolved methods. Kinetic results indicate that the tryptophan (Trp) moiety interacts with singlet molecular oxygen (O(2)((1)Delta(g))) both through chemical reaction and through physical quenching, and that the photooxidations can be compared with those of equimolecular mixtures of the corresponding free amino acids, with minimum, if any, influence of the peptide bond on the chemical reaction. This is not a common behavior in other di- and polypeptides of photooxidizable amino acids. The ratio between chemical (k(r)) and overall (k(t)) rate constants for the interaction O(2)((1)Delta(g))-dipeptide indicates that Trp-Phe and Trp-Trp are good candidates to suffer photodynamic action, with k(r)/k(t) values of 0.72 and 0.60, respectively (0.65 for free Trp). In the case of Trp-Tyr, a lower k(r)/k(t) value (0.18) has been found, likely as a result of the high component of physical deactivation of O(2)((1)Delta(g)) by the tyrosine moiety. The analysis of the photooxidation products shows that the main target for O(2)((1)Delta(g)) attack is the Trp group and suggests a much lower accumulation of kynurenine-type products, as compared with free Trp. This is possibly because of the occurrence of another accepted alternative pathway of oxidation that gives rise to 3a-oxidized hydrogenated pyrrolo[2,3-b]indoles.

Dipeptides↗
PubMed1986

Sodium-independent, hydrogen ion-dependent changes in membrane potential and conductance induced by dipeptides in Triturus enterocytes.

The effects of Na+ and pH in the medium on dipeptide transport across Triturus small intestinal brush border membrane were studied electrophysiologically. Although glycylglycine exists mainly in the zwitterionic form at pH 7.30, it induced marked depolarization in the membrane potential and reduction in the input resistance both in the presence and absence of Na+ in the medium. Similar Na+-independent depolarization and resistance change were also observed with L-carnosine. On the contrary, glycine induced membrane depolarization and reduction in the input resistance only in the presence of Na+ in the medium. When pH of the medium was lowered to 6.00, the magnitude of the depolarization induced by glycylglycine increased by 33%, while at pH 8.30, it decreased by 39%. These data indicate that dipeptide transport across the intestinal brush border membrane is coupled with H+ and has no direct interaction with Na+.

Animals↗
PubMed1996

Demonstration and characterization of dipeptide transport system activity in sheep omasal epithelium by expression of mRNA in Xenopus laevis oocytes.

Research from this laboratory has recently demonstrated that the omasal epithelium of sheep is capable of absorbing dipeptides. In order to express proteins potentially responsible for the mediated absorption of small peptides, size-fractionated poly(A)+RNA (RNA) isolated from omasal epithelial tissue of sheep (average BW 67.5 kg) were injected into defolliculated Xenopus laevis oocytes. The ability of oocytes injected with RNA or water to absorb [14C]glycyl-L-sarcosine (Gly-Sar) from media (usually pH 5.5) was compared. After 4 d (P < .02) of culture, specific RNA fractions induced an increased (P < .02) rate of Gly-Sar absorption, as compared with water-injected oocytes. The dependency of Gly-Sar uptake on the presence of a pH gradient was evaluated at pH 5.0, 5.5, 6.0, 6.5, and 7.5. Inducible uptake increased (P < .001) in the presence of increasing proton concentrations, whereas endogenous uptake of Gly-Sar decreased (P < .001). At pH 5.5, induced Gly-Sar uptake was saturable (Kt = .4 mM), but endogenous uptake was not. The specificity of Gly-Sar absorption was studied by the co-incubation of .1 mM Gly-Sar with 5 mM levels of competing substrates (pH 5.5). Induced uptake was inhibited (P < .05) 44% by carnosine, 94% by methionylglycine, and 91% by glycylleucine, but not by glycine. Incubation of RNA with DNA oligomers that were complementary to the rabbit intestinal transporter completely inhibited (P < .05) induced Gly-Sar uptake. These results indicate that sheep omasal epithelial cells express messenger RNA that encode for proteins that are capable of H(+)-dependent dipeptide transport activity.

Animals↗
PubMed1986

Inhibitors and dipeptide substrates for a microsomal tyrosylsulfotransferase from rat brain.

The sulfotransferase associated with a microsomal fraction from rat brain was previously shown to transfer sulfate groups from 3'-phosphoadenosine 5'-phosphosulfate (PAPS) to peptides derived from the cholecystokinin (CCK) molecule. Three tyrosine-containing dipeptide derivatives, i.e., Cbz-Glu-Tyr, Cbz-Gly-Tyr and Ac-Phe-Tyr are shown here to accept the [35S] sulfate group from [35S] PAPS under the action of this sulfotransferase. The sulfotransferase activity evaluated with either any of these dipeptide derivatives or CCK-8 as acceptors is similarly inhibited by a series of compounds, i.e., lipophilic polycyclic compounds like fluphenazine, tyrosine derivatives like Boc-O-benzyl-tyrosine and phenolsulfotransferase inhibitors like 4,4-di-isothiocyano 2',2'-disulfonic acid stilbene.

Animals↗
PubMed1997

Inhibition of dipeptidyl peptidase IV (CD26) by peptide boronic acid dipeptides.

Peptide boronic acid dipeptide compounds were analyzed for their ability to inhibit recombinant human dipeptidylpeptidase IV (CD26, DPPIV). Rate constants for the peptide boronates are difficult to obtain because the active boronic acid dipeptide exists in equilibrium with a cyclic inactive species in aqueous solution. Rate constants were determined for the inhibition of DPPIV using several peptide boronates at different pH values. Val-boroPro forms the most tightly bound complex with DPPIV; the first order half life for dissociation of the inactive enzyme-inhibitor complex at 23 degrees C is approximately 27 days.

Binding, Competitive↗
PubMed1997

Increases in the effects of albendazole on Echinococcus multilocularis metacestodes by the dipeptide methyl ester (Phe-Phe-OMe).

Three months after infection with Echinococcus multilocularis, Mongolian gerbils were given either the dipeptide methyl ester (Phe-Phe-OMe) or a combination of Phe-Phe-OMe plus albendazole to treat alveolar echinococcosis. Each drug was given orally at the daily dose of 50 mg/kg of body weight following various administration regimens. Histologic and ultrastructural studies of parasites recovered from infected gerbil tissues showed that the dipeptide methyl ester increases the effect of albendazole.

Albendazole↗
PubMed1976

Inhibition of the initial dipeptide synthesis of globin chains by the antibiotic enomycin in the reticulocyte lysate.

During inhibition of protein synthesis by the antibiotic enomycin at less than 5nm in the reticulocyte lysate system, polyribosomes disaggregated and the 80S ribosomes accumulated. At these concentrations little inhibition of chain elongation and release from the ribosomes was demonstrated. Enomycin caused an increase in the amount of 80S initiation complex as well as the 40S ribosomal subunit-Met-tRNA complex. The former complex could react with puromycin under the inhibiting conditions. Val-tRNA binding to the 80S ribosomes was not decreased by the antibiotic. However pactamycin-induced accumulation of the initial dipeptide (fMet-Val) was inhibited when the system was preincubated with enomycin and and fMet-tRnaf. Thus the preferential inhibition of the initial phase of protein synthesis by enomycin is made evident by its inhibition of the initial dipeptide synthesis.

Antibiotics, Antineoplastic↗
PubMed1994

1994 William J. Stickel Bronze Award. Amino acids, dipeptides, and leg skeletal muscle wound healing in diabetes.

The authors determined the effects of active amino acids and dipeptides as anabolic agents on surgically induced wound healing in lower extremity skeletal muscles in diabetic and normal rats. In order to induce diabetes, adult male Sprague-Dawley rats (200 g; 10 to 12 animals per group) were injected with streptozotocin (65 mg/kg) 30 days before the onset of the experiment. Their blood sugars were checked at this time. Each group of rats was injected with either one stimulatory amino acid or dipeptide (150 mg/kg body weight) subcutaneously in saline for 7 days and their anabolic effects (RNA, DNA, protein, and collagen contents) on lower extremity skeletal muscle wound healing determined in both diabetic and normal control groups. It is hoped that a treatment regimen will be developed using synergistic anabolic agents locally to decrease the lower extremity muscle healing time. This will enable the diabetic patient to become mobile sooner after surgery.

Amino Acids↗
PubMed2002

[Apoptosis of K562 cell induced by N-phosphoryl dipeptide methyl ester].

BACKGROUND & OBJECTIVE: Phosphorus plays a crucial role in metabolism. Some N-phosphoryl amino acids and N-phosphopeptides have important biological activities and medicinal value. The current study was designed to investigate the apoptosis of K562 cells induced by N-phosphoryl dipeptide methyl ester. METHOD: Cell growth inhibition of K562 cells induced by 15 kinds of N-phosphoryl dipeptide methyl esters was analyzed by using MTT assay. The nuclei were stained by Hoechst 33,258 and the morphologic changes were observed. DNA agarose gel electrophoresis, double-staining, and flow cytomery were used to detect early apoptosis of K562 cells. RESULT: (DIPP-L-Leu)2-L-Lys-OCH3 was the compound screened with MTT method that had better growth inhibiting activity with the IC50 of 22.66 mumol/L. Chromatin condensation and nuclear fragmentation were seen under fluorescence microscope in the cells treated with Hoechst 33,258. DNA agarose gel electrophoresis showed nuclear fragmentation (DNA ladder). Early apoptotic cells were also detected by flow cytometry. CONCLUSION: These results suggest that(DIPP-L-Leu)2-L-Lys-OCH3 could induce the apoptosis of K562 cells.

Apoptosis↗
PubMed1976

Evidence for a single common carrier for uptake of a dipeptide and a tripeptide by hamster jejunum in vitro.

This paper describes an investigation of whether a dipeptide and a tripeptide were taken up by hamster jejunum by the same transport system, or whether there was evidence of uptake by more than one transport system. The work was carried out with rings of everted hamster jejunum in vitro, under conditions of influx, using the "model" peptides glycylsarcosine, glycylsarcosylsarcosine, and glycylsarcosylsarcosylsarcosine. These peptides are all exceptionally resistant to hydrolysis, appearing intact in the rings, and the di- and tripeptide have previously been shown to be concentrated in the rings by active transport. The results showed that influx of glycylsarcosine was inhibited by glycylsarcosylsarcosine in a competitive way, and that each of the peptides was capable of causing virtually complete inhibition of influx of the other. Glycylsarcosylsarcosylsarcosine had no effect on influx of glycylsarcosine or of glycylsarcosylsarcosine. It was concluded that although the existence of multiple transport systems shared by both glycylsarcosine and glycylsarcosylsarcosine could not be ruled out, the simplest hypothesis was that both the dipeptide and the tripeptide shared a single common carrier for uptake. The tetrapeptide glycylsarcosylsarcosylsarcosine was apparently not transported by this carrier, in agreement with previous results. The possible effects of the "unstirred layer" were taken into account in considering the results and are discussed. They do not alter the conclusions reached.

Animals↗