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See detailPeptidase Activity of Beta-Lactamases
Rhazi, Noureddine ULg; Galleni, Moreno ULg; Page, Michael I. et al

in Biochemical Journal (1999), 341((Pt 2)), 409-13

Although beta-lactamases have generally been considered as being devoid of peptidase activity, a low but significant hydrolysis of various N-acylated dipeptides was observed with representatives of each ... [more ▼]

Although beta-lactamases have generally been considered as being devoid of peptidase activity, a low but significant hydrolysis of various N-acylated dipeptides was observed with representatives of each class of beta-lactamases. The kcat/Km values were below 0.1 M(-1). s(-1), but the enzyme rate enhancement factors were in the range 5000-20000 for the best substrates. Not unexpectedly, the best 'peptidase' was the class C beta-lactamase of Enterobacter cloacae P99, but, more surprisingly, the activity was always higher with the phenylacetyl- and benzoyl-d-Ala-d-Ala dipeptides than with the diacetyl- and alpha-acetyl-l-Lys-d-Ala-d-Ala tripeptides, which are the preferred substrates of the low-molecular-mass, soluble dd-peptidases. A comparison between the beta-lactamases and dd-peptidases showed that it might be as difficult for a dd-peptidase to open the beta-lactam ring as it is for the beta-lactamases to hydrolyse the peptides, an observation which can be explained by geometric and stereoelectronic considerations. [less ▲]

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See detailPeptide backbone fragmentation initiated by side-chain loss at cysteine residue in matrixassisted laser desorption/ionization in-source decay mass spectrometry
Asakawa, Daiki; Smargiasso, Nicolas ULg; Quinton, Loïc ULg et al

in Journal of Mass Spectrometry [=JMS] (2013), 48

Matrix-assisted laser desorption/ionization in-source decay (MALDI-ISD) is initiated by hydrogen transfer from matrix molecules to the carbonyl oxygen of peptide backbone with subsequent radical-induced ... [more ▼]

Matrix-assisted laser desorption/ionization in-source decay (MALDI-ISD) is initiated by hydrogen transfer from matrix molecules to the carbonyl oxygen of peptide backbone with subsequent radical-induced cleavage leading to c0/z• fragments pair. MALDI-ISD is a very powerful method to obtain long sequence tags from proteins or to do de novo sequencing of peptides. Besides classical fragmentation, MALDI-ISD also shows specific fragments for which the mechanism of formation enlightened the MALDI-ISD process. In this study, the MALDI-ISD mechanism is reviewed, and a specific mechanism is studied in details: the N-terminal side of Cys residue (Xxx-Cys) is described to promote the generation of c0 and w fragments in MALDI-ISD. Our data suggest that for sequences containing Xxx-Cys motifs, the N–Ca bond cleavage occurs following the hydrogen attachment to the thiol group of Cys side-chain. The c•/w fragments pair is formed by side-chain loss of the Cys residue with subsequent radical-induced cleavage at the N–Ca bond located at the left side (N-terminal direction) of the Cys residue. This fragmentation pathway preferentially occurs at free Cys residue and is suppressedwhen the cysteines are involved in disulfide bonds. Hydrogen attachment to alkylated Cys residues using iodoacetamide gives free Cys residue by the loss of •CH2CONH2 radical. The presence of alkylated Cys residue also suppress the formation of c•/w fragments pair via the (Cb)-centered radical, whereas w fragment is still observed as intense signal. In this case, the z• fragment formed by hydrogen attachment of carbonyl oxygen followed side-chain loss at alkylated Cys leads to a w fragment. Hydrogen attachment on peptide backbone and side-chain of Cys residue occurs therefore competitively during MALDI-ISD process. [less ▲]

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See detailPEPTIDE CLICK LABELLING WITH 1-(AZIDOMETHYL)-4-[18F]-FLUOROBENZENE AND REFERENCE COMPOUNDS SYNTHESIS ON SOLID SUPPORT
Thonon, David ULg; Paris, Jérôme ULg; Kech, Cecile et al

in Journal of Labelled Compounds and Radiopharmaceuticals (2009, July)

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See detailPeptide cross-links in bacterial cell wall peptidoglycans studied with specific endopeptidases from Streptomyces albus G
Petit, Jean-François; Munoz, Emilio; Ghuysen, Jean-Marie ULg

in Biochemistry (1966), 5(8), 2764-2776

Evidence is given for the existence of at least four types of peptide cross-linkages in lysine-containing peptidoglycans of cell walls from Gram-positive bacteria. Three kinds of such cross-linkages, by ... [more ▼]

Evidence is given for the existence of at least four types of peptide cross-linkages in lysine-containing peptidoglycans of cell walls from Gram-positive bacteria. Three kinds of such cross-linkages, by which the є-amino group of the lysine residue of one peptide subunit is joined to the carboxyl group of the terminal D-alanine of a second, have been demonstrated, namely: bridging by tri-L-alanine (Micrococcus roseus Thr(-)), by tri-L-alanine-L-threonine (M. roseus R 27), and by pentaglycine (Staphylococcus aureus Copenhagen) residues. The lytic Streptomyces SA endopeptidase hydrolyzes D-alanylglycyl linkages in S. aureus and D-alanyl-L-alanine linkages in M. roseus, i.e., at the amino terminus of the peptide bridges and at the carboxyl terminus of the peptide subunits. The lytic Streptomyces MR endopeptidase hydrolyzes L-alanyl-L-threonine linkages within the peptide bridges in M. roseus R 27 and, with a much smaller rate, L-alanyl-L-alanine linkages within the peptide bridges in M. roseus Thr(-)). A fourth kind of cross-linkage, in which no additional amino acid is involved, can also occur in the form of a direct bonding between the C-terminal alanine residue of one peptide subunit and the є-amino group of the lysine residue of a second (Micrococcus lysodeikticus). This latter alanyl-є-lysine bond is sensitive to a third lytic Streptomyces enzyme, the ML endopeptidase. A structure for the peptide moiety of the peptidoglycan of M. roseus is proposed and compared to the peptidoglycan structure in S. aureus. The present studies lend support to recent proposals dealing with the mechanism of action of penicillin. [less ▲]

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See detailPeptide G, containing the binding site of the 67-kDa laminin receptor, increases and stabilizes laminin binding to cancer cells.
Magnifico, A.; Tagliabue, E.; Buto, S. et al

in Journal of Biological Chemistry (1996), 271(49), 31179-84

We investigated the effect of peptide G, a synthetic peptide derived from the sequence of the 37-kDa laminin receptor precursor, on the interaction of laminin in two tumor cell lines one of which produces ... [more ▼]

We investigated the effect of peptide G, a synthetic peptide derived from the sequence of the 37-kDa laminin receptor precursor, on the interaction of laminin in two tumor cell lines one of which produces laminin and one of which does not. Addition of peptide G to the culture medium induced a significant increase in the amount of endogenous laminin detectable on the cell membrane of both cell lines. Moreover, pretreatment of exogenous laminin with peptide G dramatically increased laminin binding on both cell lines. Kinetics analysis of membrane-bound labeled laminin revealed a 3-fold decrease in the kd of peptide G-treated laminin compared with untreated or unrelated or scrambled peptide-treated laminin. Moreover, the affinity constant of peptide G-treated laminin increased 2-fold, with a doubling of the number of laminin binding sites, as determined by Scatchard analysis. Expression of the VLA6 integrin receptor on the cell membrane increased after incubation with peptide G-treated laminin. However, the lower binding inhibition of peptide G-treated laminin after anti-VLA6 antibody or cation chelation treatment indicates that membrane molecules in addition to integrin receptors are involved in the recognition of peptide G-modified laminin. These "new" laminin-binding proteins also mediated cell adhesion to laminin, the first step in tumor invasion. Together, the data suggest that peptide G increases and stabilizes laminin binding on tumor cells, involving surface receptors that normally do not take part in this interaction. This might explain the abundant clinical and experimental data suggesting a key role for the 67-kDa laminin receptor in the interaction between cancer cells and the basement membrane glycoprotein laminin during tumor invasion and metastasis. [less ▲]

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See detailPeptide hormones: from the transcription of the gene to the final product--a biochemical view
Martial, Joseph ULg

in Hormone Research (1989), 32(1-3), 9-12

This very short review aims at analyzing the current biochemical view of the molecular steps involved in the peptide hormone synthesis, going from the gene to the final active peptide.

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See detailPeptide inhibitors of Streptomyces DD-carboxypeptidases
Nieto, Manuel; Perkins, Harnold R.; Leyh-Bouille, Mélina et al

in Biochemical Journal (1973), 131(1), 163-171

1. Peptides that inhibit the dd-carboxypeptidases from Streptomyces strains albus G and R61 were synthesized. They are close analogues of the substrates of these enzymes. The enzymes from albus G and R61 ... [more ▼]

1. Peptides that inhibit the dd-carboxypeptidases from Streptomyces strains albus G and R61 were synthesized. They are close analogues of the substrates of these enzymes. The enzymes from albus G and R61 strains are in general inhibited by the same peptides, but the enzyme from strain R39 differs considerably. 2. The two C-terminal residues of the peptide substrates and inhibitors appear to be mainly responsible for the initial binding of the substrate to the enzymes from albus G and R61 strains. The side chain in the third residue from the C-terminus seems critical in inducing catalytic activity. 3. Experimental evidence is presented suggesting that the amide bond linking the two C-terminal residues has a cis configuration when bound to the enzymes from strains albus G and R61. 4. The peptide inhibitors are not antibiotics against the same micro-organisms. [less ▲]

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See detailA peptide mimicking the C-terminal part of the reactive center loop induces the transition to the latent form of Plasminogen Activator Inhibitor Type-1
D'Amico, Salvino ULg; Martial, Joseph ULg; Struman, Ingrid ULg

in FEBS Letters (2012), 586

Plasminogen Activator Inhibitor-1 (PAI-1) is the primary inhibitor of plasminogen activators (uPA and tPA) and thus plays a central role in fibrinolysis. The spontaneous insertion of its Reactive Centre ... [more ▼]

Plasminogen Activator Inhibitor-1 (PAI-1) is the primary inhibitor of plasminogen activators (uPA and tPA) and thus plays a central role in fibrinolysis. The spontaneous insertion of its Reactive Centre Loop (RCL) into beta-sheet A is responsible for its irreversible conversion into the inactive latent form. In this study, we used two peptides mimicking residues P14-P9 and P8-P3 of the RCL so as to understand this dynamic process. We show that both peptides inhibit the formation of PAI 1/uPA and PAI-1/tPA complexes via two different mechanisms. Targeting the N-terminal part of the loop induces the cleavage of PAI-1 by the proteases uPA/tPA while targeting its C-terminal part greatly favors the irreversible formation of latent PAI-1. [less ▲]

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See detailThe peptide N alpha-(L-alanyl-D-isoglutaminyl)-N epsilon-(D-isoasparaginyl)-L-lysyl-D-alanine and the disaccharide N-acetylglucosaminyl-beta-1,4-N-acetylmuramic acid in cell wall peptidoglycan of Streptococcus faecalis strain ATCC 9790
Ghuysen, Jean-Marie ULg; Bricas, E.; Leyh-Bouille, Martine et al

in Biochemistry (1967), 6(8), 2607-2619

A major portion of the cell wall peptidoglycan in Streptococcus faecalis is composed of the disaccharide tetrapeptide β-1,4-N-acetylglucosaminyl-N-acetylmuramyl-Nα-(L-alanyl-D-isoglutaminyl)-L-lysyl-D ... [more ▼]

A major portion of the cell wall peptidoglycan in Streptococcus faecalis is composed of the disaccharide tetrapeptide β-1,4-N-acetylglucosaminyl-N-acetylmuramyl-Nα-(L-alanyl-D-isoglutaminyl)-L-lysyl-D-alanine. The tetrapeptides are cross-linked through single D-isoasparaginyl residues extending from the C-terminal D-alanine of one tetrapeptide unit to the Nє-terminal L-lysine of another. It is the first time that the occurrence of an isoasparaginyl residue in a natural product has been described. The Streptomyces SA en-dopeptidase cleaves D-alanyl-D-isoasparaginyl linkages and is thus the first enzyme known to hydrolyze D-D peptide bonds. Treatment of the disaccharide Nα-( L-alanyl-D-isoglutaminyl)-N є-(D-isoasparaginyl)- L-lysil-D-alanine with 10 equiv of NaOH at 37° for 1 hr results in deamidation of the isoasparaginyl residue together with migration of the aspartyl-lysine peptide bond giving rise to a mixture of Nє-(β-aspartyl)- and N є-(α-aspartyl)lysyl peptides. Under the same alkaline treatment, the N-acetylmuramyl residue undergoes a lactyl elimination which results in the production of acyl peptides and a Morgan-Elson prochromogenic compound, without hydrolysis of the glycosidic linkage. This conversion, interpreted to be the result of a β elimination, also occurs in the other disaccharide peptide monomers previously isolated from Staphylococcus aureus, Micrococcus roseus, and Streptococcus pyogenes. [less ▲]

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See detailPEPTIDE-LOADED LIPOSOMES AGAINST BREAST CANCER: EFFECTIVE PENETRATION IN CELLS OF LONG CIRCULATING pH-SENSITIVE VESICLES
Ducat, Emilie ULg; Deprez, Julie ULg; Peulen, Olivier ULg et al

Poster (2010, October)

Purpose: Print3G, a peptidic antagonist of oncoprotein involved in breast cancer, could reduce the angiogenic development of breast tumors. The necessity of intravenous administration of Print3G led to ... [more ▼]

Purpose: Print3G, a peptidic antagonist of oncoprotein involved in breast cancer, could reduce the angiogenic development of breast tumors. The necessity of intravenous administration of Print3G led to the development of liposomes as drug carriers, combining the protective properties of PEG with the transfection properties of pH-sensitive lipids. The purpose of this work is to compare pegylated pH-sensitive liposomes with a classical formulation of long-circulating liposomes in terms of cellular uptake. Methods: Classical liposomes (SPC:CHOL:mPEG-750-DSPE (47:47:6 mol/mol)) and pH-sensitive liposomes (DOPE:CHEMS:CHOL: mPEG750-DSPE (43:21:30:6 mol/mol)) were compared in terms of size, charge, stability, pH-sensitivity and toxicity by inhibition of cell proliferation. Finally, confocal microscopy was used to study the cellular uptake of liposomes by three cell lines (Hs578t, WI-26 and MDA-MB-231), using 25-nitrobenzoxydiazol-cholesterol as a fluorescent marker of the vesicular membrane and rhodamine in the inner cavity of liposomes. Results: Sizes of 162.8 ± 4.6 nm and zeta potential of -9.3 ± 1.2 mV were obtained for standard liposomes (n=3) while the obtained values for pH-sensitive liposomes (n=3) were respectively of 184.8 ± 3.2 nm and -19.5 ± 2.6 mV. The two formulations were comparable in terms of shape and stability. Concerning the pH-sensitivity study, a significantly higher leakage of the encapsulated material was observed at pH 5 for pH-sensitive liposomes. Confocal pictures obtained with these vesicles on the three cell lines allowed us to visualize the colocalized red and green color with a higher concentration near the nucleus. Conclusion: Long circulating pH-sensitive liposomes are promising drug delivery systems in terms of cellular uptake. Experiments will be performed with biotinylated Print3G to assess its cellular distribution. Moreover, the accumulation of this formulation in breast tumor will be evaluated by in vivo studies. [less ▲]

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See detailPeptides As Drugs: Myth Or Reality?
Decaffmeyer, Marc ULg; Thomas, Annick ULg; Brasseur, Robert ULg

in Biotechnologie, Agronomie, Société et Environnement = Biotechnology, Agronomy, Society and Environment [=BASE] (2008), 12(1),

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See detailPeptides entrapped in biodegradable PLGA microparticles accelerate tissue repair at gastric ulcer treatment in rats
Markvicheva, E; Stashevskaya, K; Prudchenko, I et al

Conference (2007, September 09)

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See detailPeptides in membranes: tipping the balance of membrane stability.
Brasseur, Robert ULg; Pillot, T.; Lins, Laurence ULg et al

in Trends in biochemical sciences (1997), 22(5), 167-71

This review describes a class of peptides that associate with lipids in membranes and are commonly known as 'oblique-orientated peptides'. Owing to an asymmetric distribution of hydrophobic residues along ... [more ▼]

This review describes a class of peptides that associate with lipids in membranes and are commonly known as 'oblique-orientated peptides'. Owing to an asymmetric distribution of hydrophobic residues along the axis of the alpha-helix, such peptides can destabilize membranes or lipid cores, thereby facilitating such cellular processes as vesicular fusion or protein transport across subcellular compartments, as well as remodelling of lipid cores. [less ▲]

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See detailLes peptides natriurétiques: le point de vue du biologiste
LE GOFF, Caroline ULg

Conference (2015, February 26)

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See detailPeptides neurohypophysaires et dépression unipolaire: quel avenir?.
Scantamburlo, Gabrielle ULg; Pitchot, William ULg; Ansseau, Marc ULg et al

in Revue Médicale de Liège (2008), 63

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See detailPeptides obliques: Etat des lieux
Lins, Laurence ULg

Conference (2010, November 17)

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See detailThe peptidoglycan crosslinking enzyme system in Streptomyces R61, K15 and rimosus. Immunological studies
Nguyen-Distèche, Martine ULg; Frère, Jean-Marie ULg; Dusart, Jean et al

in European Journal of Biochemistry (1977), 81(1), 29-32

The exocellular DD-carboxypeptidases from Streptomyces R61, K 15, the lysozyme-releasable DD-carboxypeptidases from Streptomyces R61, K15 and rimosus, and the membrane-bound DD-carboxypeptidase of ... [more ▼]

The exocellular DD-carboxypeptidases from Streptomyces R61, K 15, the lysozyme-releasable DD-carboxypeptidases from Streptomyces R61, K15 and rimosus, and the membrane-bound DD-carboxypeptidase of Streptomyces K15 are immunologically related to each other. [less ▲]

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See detailThe peptidoglycan crosslinking enzyme system in Streptomyces strains R61, K15 and rimosus : Kinetic Coefficients Involved in the Interactions of the Membrane-Bound Transpeptidase with Peptide Substrates and β-Lactam Antibiotics
Dusart, Jean; Leyh-Bouille, Mélina; Ghuysen, Jean-Marie ULg

in European Journal of Biochemistry (1977), 81(1), 33-44

The transpeptidation reaction performed by the membranes of Streptomyces strain R61 fits the general rate equation for an enzyme-catalysed bimolecular reaction. The same membranes (E) interact with beta ... [more ▼]

The transpeptidation reaction performed by the membranes of Streptomyces strain R61 fits the general rate equation for an enzyme-catalysed bimolecular reaction. The same membranes (E) interact with beta-lactams (I) to form inactive penicillin-enzyme-membrane complexes (EI) of rather high stability, which subsequently break down (E + I leads to EI leads to E + degradation products). The enzyme is regenerated and the antibiotic is released in the form of an inactive metabolite. With benzylpenicillin, the degradation product is benzylpenicilloic acid. The reaction is heat-labile. The first step of the reaction (E + I leads to EI) is characterized by a second-order rate constant (kformation in M-1 s-1) and the second step (EI leads to E + degradation products) by a first-order rate constant (kbreakdown in s-1). The effects in vitro of various beta-lactams on the membrane-bound transpeptidase, as expressed by the relevant kformation and kbreakdown values, parallel the effects in vivo of the same antibiotics as expressed by their ability to prevent the germination and growth of conidiospores. The kinetic parameters of the transpeptidase that was solubilized with N-cetyl-N,N,N-trimethylammonium bromide with respect to its interaction with both peptide substrates and beta-lactam antibiotics are quantitatively different from those of the membrane-bound enzyme. Moreover, the solubilized enzyme fragments benzylpenicillin with formation of phenylacetylglycine, a reaction which is similar to that catalysed by the exocellular R61 enzyme. The membranes of Streptomyces strains rimosus and K15 possess an active 'classic' penicillinase. They were not studied but the kinetic coefficients of the corresponding solubilized transpeptidases were determined and compared with those of the solubilized enzyme from strain R61. [less ▲]

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