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 739 records · Page 41Linked to original sources
PubMed1996

[The dipeptide L-alanyl-L-glutamine--its preparation and therapeutic use].

L-glutamine, representing one of the principal sources of nitrogen for the organism, can be used in infusion solutions employed in clinical nutrition in the form of the dipeptide L-alanyl-L-glutamine. It can be prepared with the use of biotechnological methods, viz. the enzymic synthesis of the peptide, and fermentation preparation of L-glutamine and the proteases catalyzing the formation of the peptidic bond. Suitable producers of amino acids and enzymes are microorganisms (both bacteria and fungi). The procedures used in the preparation of the components as well as the dipeptide itself are a combination of biotransformations and fermentations.

Bacteria↗
PubMed1996

Nitrosation of tryptophan residue(s) in serum albumin and model dipeptides. Biochemical characterization and bioactivity.

Nitrosation of bovine serum albumin with acidified NaNO2 was compared to that of carboxymethyl-bovine serum albumin in which the thiol group is covalently blocked. Differential ultraviolet-visible (UV-Vis) spectroscopy and a modified Saville assay indicated that a non-cysteine residue(s) in carboxymethyl-bovine serum albumin was nitrosated. The nitrosated carboxymethyl-bovine serum albumin exhibited similar vasorelaxation activity as that observed with nitrosated bovine serum albumin. Identification of the nitrosated non-cysteine residue(s) was studied using 16 model dipeptides, each of which contained a glycyl residue and a variable residue. Using photolysis-chemiluminescence analysis, modified Saville assay, differential UV-Vis spectroscopy, and bioassays, L-glycyl-L-tryptophan (Gly-Trp) was found to be the only dipeptide that underwent significant nitrosation under these conditions. Liquid chromatography-UV-Vis spectroscopy-mass spectrometry showed that the NO group was attached to the indole nitrogen of tryptophan. Nitrosated Gly-Trp exhibited dose-dependent vasorelaxation and platelet inhibiting activity with apparent EC50 values of 1.1 +/- 0. 3 and 3.5 +/- 0.9 microM, respectively. Because N-nitroso-Gly-Trp does not release NO radical via spontaneous homolytic N-NO bond fission nor freely diffuse through cellular membranes, the ability of this compound to induce NO.-like biological effects suggests the existence of a (membrane-associated) transnitrosation system that facilitates delivery of -NO to its specific biologic target(s).

Animals↗
PubMed1996

[Glutamine dipeptide enriched nutritional solutions attenuate bacterial translocation in rats after 60% intestinal resections].

OBJECTIVE: To investigate the effects of alanyl-glutamine dipeptide (Ala-Gln) enriched parenteral nutrition solution on intestinal mucosa or gut barrier since traditional parenteral nutrition leads to bacterial translocation. METHODS: The moderate operation stress was induced by 60% resection of small intestine. Qualified rats distributed in three groups: Chow group (n = 10) received standard rat chow, PN group (n = 10) received traditional parenteral nutrition solution only, and Ala-Gln group (n = 10) received glutamine dipeptide enriched nutritional solutions (3% Ala-Gln). Rats were maintained on their respective diets for 7 days. RESULTS: Chow group and Ala-Gln group maintained serum glutamine concentration, villus height and mucosal thickness. The bacterial translocation rate in Chow group and Ala-Gln group was 20% and in PN group 70%. CONCLUSION: Results demonstrate that Ala-Gln enriched nutritional solutions maintain intestinal adaptation and gut barrier function after massive intestinal resection.

Animals↗
PubMed2004

A novel dipeptide-based HIV protease inhibitor containing allophenylnorstatine.

Dipeptide analogues incorporating allophenylnorstatine [Apns; (2S,3S)-3amino-2-hydroxy-4-phenylbutyric acid] as a transition state mimic at the scissile bond were designed and synthesized in the hope of obtaining a novel KNI series of HIV protease inhibitors. The precursors, N-P2'-3-(2S,3S)-3-(tert-butyloxy-carbonyl)amino-2-hydroxy-4-phenylbutanoyl)-5,5-dimethylthiazolidine-4-carboxamide (N-Boc-Apns-Dmt-P2') 4a-p were prepared by deprotection of the synthones N-P2'-(tert-butyloxycarbonyl)-5,5-dimethylthiazolidine-4-carboxamide (Boc-Dmt-P2') 2a-p, then coupling with (2S,3S)3-(tert-butyloxycarbonyl)amino-2-hydroxy-4-phenylbutanoic acid (N-Boc-Apns-OH) 3. The deprotected intermediates 4 were coupled with the activated carboxyl groups of the P2 ligands to afford the target dipeptides. In this work, we fixed at the P2 site either a 2,6-dimethylphenoxyacetyl or a 3-hydroxy-2-methylbenzoyl group. Substitutes at the P2' site were varied to afford the members of the series 7 and 8. Improved activity of most of the members of series 8 relative to their analogues of series 7 can be partially attributed to the differences in the structures of the P2 moieties. Positional isomerism in the P2' moieties significantly affected the activity and polarity of the target.

Chromatography, High Pressure Liquid↗
PubMed1983

Opposite effects of the synthetic immunomodulator, muramyl dipeptide, on rejection of mouse skin allografts.

The influence of muramyl dipeptide (N-acetylmuramyl-L-alanyl-D-isoglutamine) on the rejection of mouse skin allografts was investigated. While the 0.1-mg dose administered on days 7, 6, 5 prior to transplantation caused significant prolongation of the graft survival, the 0.5-mg dose administered on days 3, 2, 1 prior to transplantation resulted in remarkable augmentation of the graft rejection. The present results support the view that muramyl dipeptide can induce both stimulatory and suppressive immune mechanisms, depending on the treatment regimen.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1997

Resolution of acylated dipeptide stereoisomers by capillary electrophoresis using sulfobutylether derivatized beta-cyclodextrin.

The separation of enantiomerically and diastereomerically related stereoisomers of acylated Asp-Phe dipeptides was explored using capillary electrophoresis (CE). This series of dipeptides included the alpha-L,L parent compound and the three other potential Asp containing stereoisomers (alpha-D,D, alpha-L,D, and alpha-D,L), as well the four possible isoAsp containing stereoisomers (beta-L,L, beta-D,D, beta-L,D and beta-D,L). The separation of these substances was explored using both neutral and charged cyclodextrins as the stereoisomer selector added to the running electrolyte. The major experimental parameters investigated included pH, the cyclodextrin type, and the cyclodextrin concentration. Due to differences in the pKa values of the carboxylic acid groups, adjustment of the separation buffer to between pH 3.0 and 4.0 provided for sufficient electrophoretic mobility differences to result in excellent separations of the diastereomerically related peptides in this pH region. The resolution of the enantiomerically related peptide stereoisomers was accomplished using low concentrations (1 mM) of the anionic cyclodextrin derivative, sulfobutylether-beta-cyclodextrin (SBE-beta-CD). This negatively charged cyclodextrin was found to be superior for the resolution of the enantiomerically related peptides as compared to native beta-cyclodextrin or the neutral derivatives, dimethyl beta-cyclodextrin and hydroxypropyl beta-cyclodextrin. An alternative approach using anionic or neutral surfactants in conjunction with the SBE-beta-CDs was also explored and found to be successful but problematic.

Acylation↗
PubMed2005

Differentiation of Boc- alpha,beta- and beta,alpha-peptides and a pair of diastereomeric beta,alpha-dipeptides by positive and negative ion electrospray tandem mass spectrometry (ESI-MS/MS).

Positive and negative ion electrospray ionization (ESI) tandem mass spectral study of a new series of hybrid peptides, viz, BocN-alpha,beta-peptides and BocN-beta,alpha-peptides, synthesized from C-linked carbo-beta3-amino acids [Caa (S)] and L-Ala has been carried out. The alpha,beta-peptides have been differentiated from beta,alpha-peptides by the collision-induced dissociation (CID) of [M + H]+ and [M - H]- ions in positive and negative ion ESI-MS respectively. The fragment ion [M + H - C(CH3)3 + H]+ formed from [M + H]+ ions by the loss of 2-methyl-prop-2-ene in alpha,beta-peptides with L-Ala at the N-terminus is insignificant or totally absent for beta,alpha-peptides which have the Caa (S) at N-terminus. The fragment ion [M - H-C(CH3)3OH - HNCO]- formed from [M - H]- of beta,alpha-peptide acids is totally absent for alpha,beta-peptide acids. This has been attributed to the absence of the beta-methylene group in alpha,beta-peptides, and the participation of the beta-methylene group in the loss of HNCO in beta,alpha-peptide acids is confirmed by the deuteration experiments. The CID of [M + H-Boc + H]+ ions of these peptides also produce characteristic fragmentation. In the CID spectra of alpha,beta-peptides, the b(n)+ ions and the resulting y(n)+ ions occur at a mass difference of 243 and 71 Da corresponding to the successive losses of Caa and L-Ala, whereas a mass difference of 71 and 243 Da is observed for beta,alpha-peptides. In contrast to the CID of protonated peptides, the CID of [M - H]- ions of the alpha,beta- and beta,alpha-peptide acids do not give b(n)- ions and show abundant z(n) (-) ions. Further, a pair of diastereomeric dipeptide esters and acids have been distinguished by the CID of [M + H]+ ions. The loss of 2-methyl-prop-2-ene is more pronounced for Boc-NH-Caa(R)-D-Ala-OCH3 (21) and Boc-NH-Caa(R)-D-Ala-OH (23) with Caa (R) at the N-terminus, whereas it is totally absent for Boc-NH-Caa (S)-D-Ala-OCH3 (22) and Boc-NH-Caa(S)-D-Ala-OH (24) peptides, which have Caa (S) at the N-terminus. Thus, on the basis of our previous and present studies, we propose that the CID of [M + H]+ ions provides a simple and useful method for distinguishing the configuration of Caa (S or R) at the N-terminus of BocN-carbo beta,alpha- and beta,beta-dipeptides.

Molecular Structure↗
PubMedDate not supplied

Sweet and bitter taste: structure and conformations of two aspartame dipeptide analogues.

The synthesis and X-ray diffraction analysis of two dipeptide taste ligands have been carried out as part of our study of the molecular basis of taste. The compounds L-aspartyl-D-alpha-methylphenylalanine methyl ester [L-Asp-D-(alpha Me)Phe-OMe] and L-aspartyl-D-alanyl-2,2,5, 5-tetramethylcyclopentanyl ester [L-Asp-D-Ala-OTMCP] elicit bitter and sweet taste, respectively. The C-terminal residues of the two analogues adopt distinctly different conformations in the solid state. The aspartyl moiety assumes the same conformation found in other dipeptide taste ligands with the side-chain carboxylate and the amino groups forming a zwitterionic ring with a conformation defined by psi, chi 1 = 157.7 degrees, -61.5 degrees for L-Asp-D-Ala-OTMCP and 151.0 degrees, -68.8 degrees for L-Asp-D-(alpha Me)Phe-OMe. In the second residue, a left-handed helical conformation is observed for the (alpha Me)Phe residue of L-Asp-D-(alpha Me)Phe-OMe with phi 2 = 49.0 degrees and psi 2 = 47.9 degrees, while the Ala residue of L-Asp-D-Ala-OTMCP adopts a semi-extended conformation characterized by dihedral angles phi 2 = 62.8 degrees and psi 2 = -139.9 degrees. The solid-state structure of the bitter L-Asp-D-(alpha Me)Phe-OMe is extended: while the crystal structure of the sweet L-Asp-D-OTMCP roughly adopts the typical L-shaped structure shown by other sweeteners. The data of L-Asp-D-(alpha Me)Phe-OMe are compared with those of its diastereoisomer L-Asp-L-(alpha Me)Phe-OMe. Conformational analysis of the two taste ligands in solution by NMR and computer simulations agrees well with our model for sweet and bitter tastes.

Aspartame↗
PubMed2005

Preparation and reactivity of aminoacyl pyroglutamates. Facile synthesis of 10-membered-ring cyclic dipeptides derived from 1,4-diaminobutyric and glutamic acids.

A number of protected proline-containing dipeptides Boc-Xaa-Pro-OBu(t) were converted via epimerization-free oxidation with RuO4 to dipeptides with an internal pyroglutamic acid residue, Boc-Xaa-Glp-OBu(t). The latter were subjected to oxidative Hoffman-type rearrangement induced by PhI[OC(O)CF3]2 to give N-(aminoacyl)-pyroglutamates. The behavior of these derivatives under basic conditions was studied, and for two such a derivatives an aminoacyl incorporation reaction was observed, producing otherwise poorly accessible 10-membered-ring dilactams derived from 1,4-diaminobutyric and glutamic acids in practicable yields.

Aminoacylation↗
PubMed1996

Modulation of expression of class II MHC and CD40 molecules in murine B cells by various muramyl dipeptides.

Several compounds of the MDP (muramyl dipeptide) series which have the capacity to enhance the immune response to antigens exerted a comitogenic effect on murine splenic B cells. The expression of surface class II major histocompatibility and CD40 antigens was used to more accurately evaluate the comparative influence of the synthetic agents on mature B cells and on the pre-B cell line 70Z/3. MDP and two adjuvant-active analogs enhanced expression of both surface molecules and increased the response to lipopolysaccharide (LPS) or interferon-gamma (IFN-gamma) in splenic B cells. The three synthetic adjuvants alone did not lead to expression of cell-surface I-Ad or CD40 in 70Z/3 cells, indicating that they were unable by themselves to achieve differentiation of pre-B cells to a mature B cell phenotype. However, they increased the CD40 level induced by treatment with LPS. In this cell line, the response (CD40 protein and mRNA) to IFN-gamma was strongly increased by MDP but not by the two other compounds. Actually, MDP was the only adjuvant among the three compounds to functionally activate the transcription factor NF-kappaB, to induce kappa transcription, and to stimulate surface kappa light-chain expression in 70Z/3 cells. The response to muramyl dipeptides in mature splenic B cells could appear independent of the transcription factor.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed2000

Low Molecular Weight Gelators for Organic Fluids: Gelation Using a Family of Cyclo(dipeptide)s.

Simple cyclo(dipeptide)s consisting of diverse amino acids are able to cause physical gelation in a wide variety of organic fluids, including edible oils, glyceryl esters, alcohols, and aromatic molecules. Minimum gel concentrations, FTIR spectroscopy, NMR spectroscopy, and electron micrograph are used to characterize gel phenomenon. The intermolecular hydrogen bonding between N-H and C=O in cyclo(dipeptide)s plays an important role in gelation. FTIR and X-ray diffraction data suggest that the aggregate responsible for gel is an assembly of hydrogen-bonded molecular ladders, which are initially formed from numerous molecules through intermolecular hydrogen bonding. The ladder-like aggregates are intertwined and interlocked, and finally immobilize organic fluids. The gelation ability is discussed in connection with the three-component solubility parameters of solvents. Copyright 2000 Academic Press.

Journal Article↗
PubMed1995

Dipeptide transport in barley mesophyll vacuoles.

The transport of [14C]glycyl-glycine (Gly-Gly) across the tonoplast of isolated barley vacuoles has been characterized. Uptake of the dipeptide Gly-Gly into barley mesophyll vacuoles was strongly increased by the addition of ATP, while Mg2+ inhibited the ATP-dependent fluxes. Inhibition of the vacuolar proton pump by bafilomycin or dissipation of the delta pH had no effect on the ATP-dependent Gly-Gly uptake. Only the non-hydrolysable ATP analogue 5'-adenylylimidodiphosphate could partially substitute for ATP; ADP, GTP and UTP had no effect. Transport of Gly-Gly was saturable exhibiting an apparent Km of 49 +/- 5 mM. Uptake was inhibited by the sulphydryl reagents N-ethylmaleimide and p-chloromercuribenzenesulphonic acid. When present at 30 mM, various dipeptides as well as tri-glycine inhibited Gly-Gly (10 mM) uptake by 30-50%, whereas 5 mM phenylalanine was able to inhibit Gly-Gly uptake almost completely. Comparison with published data suggests that Gly-Gly is transferred across the tonoplast by the same system as several amino acids and inorganic ions.

Adenosine Triphosphate↗
PubMed1992

Differences in proinflammatory activity of several immunomodulatory derivatives of muramyl dipeptide (MDP) with special reference to the mechanism of the MDP effects.

Immunomodulatory agents, muramyl dipeptide (MDP) and several of its analogues, i.e. adamantylamide dipeptide, murametide, murabutide and their glucosaminylated derivatives, were tested for edemagenic activity in rats. Given systemically in aqueous solutions, only MDP and glucosaminylated MDP, at the dose of 3 mg/kg (s.c. or p.o.), were found to produce edematous swelling of the paws. Local (intra-pad) application of MDP was more effective than the systemic one. Supernatants of macrophages, in vitro cultured in presence of MDP, caused the swelling as well. The edema was of a transient nature. After reaching the maximum severity (about 6 h after injection of MDP solution or 1 h after macrophage supernatants), it was subsiding and disappeared completely within approximately 6 days after cessation of the treatment. It was found that this type of rat paw edema is probably a prostaglandin-dependent consequence of macrophage activation. Hypotheses on the involvement of immunoregulatory cytokines, and possible chemical structure-inflammatory activity relationships have been suggested.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1996

The distribution of carnosine and related dipeptides in rat and human tissues.

Carnosine and anserine are present in high concentrations in most skeletal muscles. In addition, carnosine and homocarnosine have been detected in brain and cardiac muscle. Other tissues have been found to be devoid of these histidine-containing dipeptides. However, Flancbaum et al. reported that carnosine was present in every rodent and human tissue analyzed. These authors postulated that carnosine serves as a non-mast cell reservoir for histidine which becomes available for histamine synthesis during periods of physiological stress. We have analyzed many rat and human tissues using an immunohistochemical procedure. Carnosine and related dipeptides were detected in skeletal muscle, cardiac muscle and brain, but not in kidney, liver, lung or several other organs. These negative results seem valid since the immunoassay gave positive staining in the tissues generally known to contain carnosine.

Aged↗
PubMed1996

Pericholangitis in a rabbit colitis model induced by injection of muramyl dipeptide emulsified with a long-chain fatty acid.

Rabbit colitis has been induced by injection of muramyl dipeptide emulsified with a long-chain fatty acid. The muramyl dipeptide emulsion was injected submucosally at six portions of the rectum and colon, 10 cm proximal to the anus, using a flexible endoscope. Six rabbits were injected six times every 2 weeks and subsequently killed 2 weeks after the last injection. The histological changes of the colon that occurred in all 6 rabbits were mononuclear cell and histiocyte infiltration with sporadic eosinophils, transmural infiltration, and well-maintained goblet cell populations. These changes were different in degree. In 4 of 6 rabbits histological examination of the liver showed pericholangitis and periductal fibrosis mimicking the pericholangitis frequently seen in patients with inflammatory bowel disease. Fibrosis bridging between the portal and portal veins occurred in 2 rabbits, and noncaseating granuloma was seen in 1 rabbit. These histological changes in our model have led to the suggestion that continuous stimulation with bacterial cell wall fragments may be involved in chronic intestinal inflammation and extraintestinal manifestations such as pericholangitis.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1996

Extraintestinal manifestations of granulomatous enterocolitis induced in rabbits by long-term submucosal administration of muramyl dipeptide emulsified with Freund's incomplete adjuvant.

We examined whether extraintestinal manifestations of granulomatous enterocolitis in rabbits might be produced by the long-term administration of muramyl dipeptide which represents the basic fragment of the bacterial cell wall, emulsified with Freund's incomplete adjuvant. Muramyl dipeptide emulsion was injected submucosally at six sites in the rectum and colon, 10 cm proximal to the anus, each time with a flexible endoscope. Seven rabbits were injected nine times or more every month, and all were sacrificed 1 month after the last injection. The histological changes in the colon in the seven rabbits were mononuclear cell infiltration, epithelioid granulomas, granulomatous lesion, and denuded and regenerative epithelia, although the changes differed in degree. In five of the seven rabbits, histological examination of the liver showed pericholangitis and periductal fibrosis, findings analogous to sclerosing cholangitis in patients with inflammatory bowel disease. In four of the seven rabbits, fibrosis bridging mainly between portal and portal veins, and, in places, between portal and central veins, was seen. Two of the seven rabbits developed polyarthritis. The histological changes in our model suggest that continuous stimulation with bacterial cell wall fragments may be involved in the extraintestinal manifestations of chronic intestinal inflammation such as that seen in inflammatory bowel disease.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1996

Effect of essential trace metal on bone metabolism in the femoral-metaphyseal tissues of rats with skeletal unloading: comparison with zinc-chelating dipeptide.

The effect of essential trace metals on bone metabolism was investigated in the femoral-metaphyseal tissues obtained from skeletal-unloaded rats. Skeletal unloading was designed by using the model of hindlimb suspension in rats; the animals were fed for 4 days with the unloading. Femoral-metaphyseal tissues were cultured for 24 hours in a medium containing either vehicle (control), nickel, manganese, cobalt, copper, zinc, or zinc-chelating dipeptide (beta-alanyl-L-histidinato zinc; AHZ) in the concentration range of 10(-6) to 10(-4) M. Bone biochemical components (alkaline phosphatase activity, glucose consumption, and DNA content) were significantly decreased by skeletal unloading. The presence of zinc sulfate or AHZ (10(-5) and 10(-4) M) caused a significant increase of alkaline phosphatase activity in the bone tissues from unloaded rats. This effect was not seen by nickel, manganese, cobalt and copper (10(-6) to 10(-4) M). The culture medium glucose was clearly consumed by the bone tissues. This consumption was inhibited by nickel, manganese, or copper (10(-5) and 10(-4) M), while cobalt, zinc, and AHZ had no effect. DNA content in the bone tissues from unloaded rats was significantly increased by all metal compounds (10(-5) M). The effect of AHZ on bone components was greater than zinc sulfate. The AHZ (10(-5) M)-increased alkaline phosphatase activity in the bone tissues from unloaded rats was clearly blocked by the presence of cycloheximide (10(-6) M), staurosporine (10(-7) M), dibucaine (10(-4) M), or okadaic acid (10(-7) M). The present study demonstrates that, of various essential trace metals, zinc compounds have an unique anabolic effect on bone metabolism in the femoral-metaphyseal tissues of rats with skeletal unloading. Zinc-chelating dipeptide may stimulate bone protein synthesis through the mechanism that is involved in protein kinases.

Alkaline Phosphatase↗
PubMed1979

Structure of a Gla-containing dipeptide. The crystal structure of (+/-)-N-carbobenzoxy-(gamma,gamma'-DI-tertbutyl)-gamma-carboxyglutamylglycine ethyl ester.

The crystal and molecular structure of a dipeptide containing a blocked gamma-carboxyglutamyl (Gla) residue is presented. Two intermolecular hydrogen bonds link the amides with carbonyl groups in the dipeptide backbone, but the protected gamma-carboxy groups on the modified glutamic acid are not hydrogen bonded.

1-Carboxyglutamic Acid↗