References of "Frère, Jean-Marie"
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See detailA collapsed intermediate with nonnative packing of hydrophobic residues in the folding of TEM-1 beta-lactamase
Vanhove, M.; Lejeune, Annabelle ULg; GUILLAUME, G. et al

in Biochemistry (1998), 37(7), 1941-1950

The kinetics of refolding of TEM-1 beta-lactamase from solution in guanidine hydrochloride have been investigated on the manual and stopped-flow mixing time scales. The kinetics of change of far-UV ... [more ▼]

The kinetics of refolding of TEM-1 beta-lactamase from solution in guanidine hydrochloride have been investigated on the manual and stopped-flow mixing time scales. The kinetics of change of far-UV circular dichroism and of intrinsic and ANS fluorescence have been compared with changes in the quenching of fluorescence by acrylamide as a probe of the accessibility of solvent to tryptophan. The binding of ANS points to hydrophobic collapse in the very early stages of folding which take place in the burst phase. This is accompanied by regain of 60-65% of-native ellipticity, indicating formation of a significant proportion of secondary structure, Also in the burst phase, the tryptophan residues, which are largely exposed to solvent in the native protein, become less accessible to acrylamide, and the intrinsic fluorescence increases markedly. An early intermediate is thus formed in which tryptophan is more buried than in the native protein. Further intermediates are formed over the next 20 s. Quenching by acrylamide increases during this period, as the transient nonnative state is disrupted and the tryptophan residue(s) become(s) reexposed to solvent, The two slowest phases are determined by the isomerization of incorrect prolyl isomers, but double jump tryptophan fluorescence and acrylamide quenching experiments show little, if any, effect of proline isomerization on the earlier phases, Hydrophobic collapse thus occurs to a folding intermediate in which there is a nonnative element of structure which has to rearrange in the later steps of folding, resulting in a nonhierarchical folding pathway. The C-terminal W290 is suggested as being involved in the nonnative intermediate. beta-Lactamase provides further evidence for the occurrence of nonnative intermediates in protein folding. [less ▲]

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See detailInducible class C beta-lactamases produced by psychrophilic bacteria
Pierrard, Annick ULg; Ledent, P.; Docquier, J. D. et al

in FEMS Microbiology Letters (1998), 161

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See detailRésistance bactérienne aux beta-lactamines
Charlier, Paulette ULg; Coyette, Jacques ULg; Dehareng, Dominique ULg et al

in Medecine Sciences : M/S (1998), 14(5), 544-555

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See detailSite-Directed Mutagenesis of the Actinomadura R39 DD-Peptidase
Zhao, GuoHua; Duez, Colette ULg; Forceille, Christine et al

in Biochemical Journal (1997), 327(2), 377-381

The role of various residues in the conserved structural elements of the Actinomadura R39 penicillin-sensitive dd-peptidase has been studied by site-directed mutagenesis. Replacement of Ser-298 of the ... [more ▼]

The role of various residues in the conserved structural elements of the Actinomadura R39 penicillin-sensitive dd-peptidase has been studied by site-directed mutagenesis. Replacement of Ser-298 of the 'SDN loop' by Ala or Gly significantly decreased the kcat/Km value for the peptide substrate, but only by a factor of 15 and had little effect on the other catalytic properties. Mutations of Asn-300 of the same loop and of Lys-410 of the KTG triad yielded very unstable proteins. However, the N300S mutant could be purified as a fusion protein with thioredoxin that exhibited decreased rates of acylation by the peptide substrate and various cephalosporins. Similar fusion proteins obtained with the N300A, K410H and K410N mutants were unstable and their catalytic and penicillin-binding properties were very strongly affected. In transpeptidation reactions, the presence of the acceptor influenced the kcat/Km values, which suggested a catalytic pathway more complex than a simple partition of the acyl-enzyme between hydrolysis and aminolysis. These results are compared with those obtained with two other penicillin-sensitive enzymes, the Streptomyces R61 dd-peptidase and Escherichia coli penicillin-binding protein (PBP) 5. [less ▲]

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See detailThe Bimodular G57-V577 Polypeptide Chain of the Class B Penicillin-Binding Protein 3 of Escherichia Coli Catalyzes Peptide Bond Formation from Thiolesters and Does Not Catalyze Glycan Chain Polymerization from the Lipid II Intermediate
Adam, Maggy; Fraipont, Claudine ULg; Rhazi, Noureddine ULg et al

in Journal of Bacteriology (1997), 179(19), 6005-6009

Because the specificity profile of the membrane anchor-free G57-V577 penicillin-binding protein 3 (PBP3) of Escherichia coli for a large series of beta-lactam antibiotics is similar to that of the full ... [more ▼]

Because the specificity profile of the membrane anchor-free G57-V577 penicillin-binding protein 3 (PBP3) of Escherichia coli for a large series of beta-lactam antibiotics is similar to that of the full-size membrane-bound PBP, the truncated PBP is expected to adopt the native folded conformation. The truncated PBP3 functions as a thiolesterase. In aqueous media and in the presence of millimolar concentrations of a properly structured amino compound, it catalyzes the aminolysis of the thiolester until completion, suggesting that the penicillin-binding module of PBP3 is designed to catalyze transpeptidation reactions. In contrast, the truncated PBP3 is devoid of glycan polymerization activity on the E. coli lipid II intermediate, suggesting that the non-penicillin-binding module of PBP3 is not a transglycosylase. [less ▲]

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See detailUnexpected Influence of a C-Terminal-Fused His-Tag on the Processing of an Enzyme and on the Kinetic and Folding Parameters
Ledent, Philippe; Duez, Colette ULg; Vanhove, Marc et al

in FEBS Letters (1997), 413(2), 194-196

The addition of a poly-His C-terminal extension, designed to facilitate the purification of the protein, to the beta-lactamase of a thermophilic Bacillus licheniformis strain modified the site of action ... [more ▼]

The addition of a poly-His C-terminal extension, designed to facilitate the purification of the protein, to the beta-lactamase of a thermophilic Bacillus licheniformis strain modified the site of action of the signal peptidase. This resulted in the secretion of a protein with a different N-terminus, showing that this type of protein engineering might not always be as 'neutral' as generally assumed. (C) 1997 Federation of European Biochemical Societies. [less ▲]

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See detailSite-directed mutagenesis of glutamate 166 in two beta-lactamases. Kinetic and molecular modeling studies.
Guillaume, Gilliane; Vanhove, M; Lamotte-Brasseur, J et al

in Journal of Biological Chemistry (1997), 272(9), 5438-44

The catalytic pathway of class A beta-lactamases involves an acyl-enzyme intermediate where the substrate is ester-linked to the Ser-70 residue. Glu-166 and Lys-73 have been proposed as candidates for the ... [more ▼]

The catalytic pathway of class A beta-lactamases involves an acyl-enzyme intermediate where the substrate is ester-linked to the Ser-70 residue. Glu-166 and Lys-73 have been proposed as candidates for the role of general base in the activation of the serine OH group. The replacement of Glu-166 by an asparagine in the TEM-1 and by a histidine in the Streptomyces albus G beta-lactamases yielded enzymes forming stable acyl-enzymes with beta-lactam antibiotics. Although acylation of the modified proteins by benzylpenicillin remained relatively fast, it was significantly impaired when compared to that observed with the wild-type enzyme. Moreover, the E166N substitution resulted in a spectacular modification of the substrate profile much larger than that described for other mutations of Omega-loop residues. Molecular modeling studies indicate that the displacement of the catalytic water molecule can be related to this observation. These results confirm the crucial roles of Glu-166 and of the "catalytic" water molecule in both the acylation and the deacylation processes. [less ▲]

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See detailThe Penicillin sensory transducer, blar, involved in the inducibility of beta-lactamase synthesis in bacillus licheniformis is embedded in the plasma membrane via a four-alpha-helix bundle
Hardt, Karin; Joris, Bernard ULg; Lepage, Sophie et al

in Molecular Microbiology (1997), 23(5), 935-944

Prediction studies, conformational analyses and membrane-topology mapping lead to the conclusion that the penicillin sensory transducer, BlaR, involved in the inducibility of beta-lactamase synthesis in ... [more ▼]

Prediction studies, conformational analyses and membrane-topology mapping lead to the conclusion that the penicillin sensory transducer, BlaR, involved in the inducibility of beta-lactamase synthesis in Bacillus licheniformis, is embedded in the plasma membrane bilayer via four transmembrane segments TM1-TM4 that forma four-alpha-helix bundle. The extracellular 262-amino-acid-residue polypeptide, S340-R601, that is fused at the carboxy end of TM4, possesses the amino acid sequence signature of a penicilloyl serine transferase. It probably functions as penicillin sensor. As an independent entity, this polypeptide behaves as a high-affinity penicillin-binding protein. As a component of the full-size BlaR, it adopts a different conformation presumably because of interactions with the extracellular 63-amino-acid-residue P53-S115 loop that connects TM2 and TM3. Reception of the penicillin-induced signal requires a precise conformation of the sensor but it does not involve penicilloylation of the serine residue S402 of motif STYK. Signal transmission through the plasma membrane by the four-alpha-helix bundle may proceed in a way comparable to that of the aspartate receptor, Tar. Signal emission in the cytosol by the intracellular 189-amino-acid-residue Y134-K322 loop that connects TM3 and TM4, may proceed via the activation of a putative metallopeptidase. [less ▲]

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See detailThree hTIM mutants that provide new insights on why TIM is a dimer
Mainfroid, Véronique; Terpstra, Peter; Beauregard, Marc et al

in Journal of Molecular Biology (1996), 257(2), 441-56

Human triosephosphate isomerase (hTIM), a dimeric enzyme, was altered by site-directed mutagenesis in order to determine whether it can be dissociated into monomers. Two hTIM mutants were produced, in ... [more ▼]

Human triosephosphate isomerase (hTIM), a dimeric enzyme, was altered by site-directed mutagenesis in order to determine whether it can be dissociated into monomers. Two hTIM mutants were produced, in which a glutamine residue was substituted for either Met14 or Arg98, both of which are interface residuces. These substitutions strongly interfere with TIM subunit association, since these mutant TIMs appear to exist as compact monomers in dynamic equilibrium with dimers. In kinetic studies, the M14Q mutant exhibits significant catalytic activity, while the R98Q enzyme is inactive. The M14Q enzyme is nevertheless much less active than unmutated hTIM. Moreover, its specific activity is concentration dependent, suggesting a dissociation process in which the monomers are inactive. In order to determine the conformational stability of the wild-type and mutant hTIMs, unfolding of all three enzymes was monitored by circular dichroism and tryptophan fluorescence spectroscopy. In each case, protein stability is concentration dependent, and the unfolding reaction is compatible with a two-state model involving the native dimer and unfolded monomers. The conformational stability of hTIM, as estimated according to this model, is 19.3 (+/-0.4) kcal/mol. The M14Q and R98Q replacements significantly reduce enzyme stability, since the free energies of unfolding are 13.8 and 13.5 (+/- 0.3) kcal/mol respectively, for the mutants, A third mutant, in which the M14Q and R98Q replacements are cumulated, behaves like a monomer. The stability of this mutant is not concentration-dependent, and the unfolding reaction is assigned to a transition from a folded monomer to an unfolded monomer. The conformational stability of this double mutant is estimated 2.5 (+/-0.1) kcal/mol. All these data combined suggest that TIM monomers are thermodynamically unstable. This might explain why TIM occurs only as a dimer. [less ▲]

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See detailThe catalytic mechanism of beta-lactamases: NMR titration of an active-site lysine residue of the TEM-1 enzyme.
Damblon, Christian ULg; Raquet, X.; Lian, L. Y. et al

in Proceedings of the National Academy of Sciences of the United States of America (1996), 93(5), 1747-52

Beta-Lactamases are widespread in the bacterial world, where they are responsible for resistance to penicillins, cephalosporins, and related compounds, currently the most widely used antibacterial agents ... [more ▼]

Beta-Lactamases are widespread in the bacterial world, where they are responsible for resistance to penicillins, cephalosporins, and related compounds, currently the most widely used antibacterial agents. Detailed structural and mechanistic understanding of these enzymes can be expected to guide the design of new antibacterial compounds resistant to their action. A number of high-resolution structures are available for class A beta-lactamases, whose catalytic mechanism involves the acylation of a serine residue at the active site. The identity of the general base which participates in the activation of this serine residue during catalysis has been the subject of controversy, both a lysine residue and a glutamic acid residue having been proposed as candidates for this role. We have used the pH dependence of chemical modification of epsilon-amino groups by 2,4,6,-trinitrobenzenesulfonate and the pH dependence of the epsilon-methylene 1H and 13C chemical shifts (in enzyme selectively labeled with [epsilon-13C]lysine) to estimate the pKa of the relevant lysine residue, lysine-73, of TEM-1 beta-lactamase. Both methods show that the pKa of this residue is > 10, making it very unlikely that this residue could act as a proton acceptor in catalysis. An alternative mechanism in which this role is performed by glutamate-166 through an intervening water molecule is described. [less ▲]

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See detailSaturation of Penicillin-Binding Protein 1 by Beta-Lactam Antibiotics in Growing Cells of Bacillus Licheniformis
Lepage, Sylvie ULg; Lakaye, Bernard ULg; Galleni, Moreno ULg et al

in Molecular Microbiology (1995), 16(2), 365-72

With the help of a new highly sensitive method allowing the quantification of free penicillin-binding proteins (PBPs) and of an integrated mathematical model, the progressive saturation of PBP1 by various ... [more ▼]

With the help of a new highly sensitive method allowing the quantification of free penicillin-binding proteins (PBPs) and of an integrated mathematical model, the progressive saturation of PBP1 by various beta-lactam antibiotics in growing cells of Bacillus licheniformis was studied. Although the results confirmed PBP1 as a major lethal target for these compounds, they also underlined several weaknesses in our present understanding of this phenomenon. In growing cells, but not in resting cells, the penicillin target(s) appeared to be somewhat protected from the action of the inactivators. In vitro experiments indicated that amino acids, peptides and depsipeptides mimicking the peptide moiety of the nascent peptidoglycan significantly interfered with the acylation of PBP1 by the antibiotics. In addition, the level of PBP1 saturation at antibiotic concentrations corresponding to the minimum inhibitory concentrations was not constant, suggesting that additional, presently undiscovered, factors might be necessary to account for the experimental observations. [less ▲]

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See detailAmpd, Essential for Both Beta-Lactamase Regulation and Cell Wall Recycling, Is a Novel Cytosolic N-Acetylmuramyl-L-Alanine Amidase
Jacobs, Christine ULg; Joris, Bernard ULg; Jamin, M. et al

in Molecular Microbiology (1995), 15(3), 553-9

In enterobacteria, the ampD gene encodes a cytosolic protein which acts as a negative regulator of beta-lactamase expression. It is shown here that the AmpD protein is a novel N-acetylmuramyl-L-alanine ... [more ▼]

In enterobacteria, the ampD gene encodes a cytosolic protein which acts as a negative regulator of beta-lactamase expression. It is shown here that the AmpD protein is a novel N-acetylmuramyl-L-alanine amidase (E.C.3.5.1.28) participating in the intracellular recycling of peptidoglycan fragments. Surprisingly, AmpD exhibits an exclusive specificity for substrates containing anhydro muramic acid. This anhydro bond is mainly found in the peptidoglycan degradation products formed by the periplasmic lytic transglycosylases and thus might behave as a 'recycling tag' allowing the enzyme to distinguish these fragments from the newly synthesized peptidoglycan precursors. The AmpD substrate (or substrates) which accumulates in the absence of the corresponding enzymatic activity acts as an intracellular positive effector for beta-lactamase expression and might represent an element of a communication network between the chromosome and the cell wall peptidoglycan. [less ▲]

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See detailContribution of Mutant Analysis to the Understanding of Enzyme Catalysis: The Case of Class a Beta-Lactamases
Matagne, André ULg; Frère, Jean-Marie ULg

in Biochimica et Biophysica Acta (1995), 1246(2), 109-27

Class A beta-lactamases represent a family of well studied enzymes. They are responsible for many antibiotic resistance phenomena and thus for numerous failures in clinical chemotherapy. Despite the facts ... [more ▼]

Class A beta-lactamases represent a family of well studied enzymes. They are responsible for many antibiotic resistance phenomena and thus for numerous failures in clinical chemotherapy. Despite the facts that five structures are known at high resolution and that detailed analyses of enzymes modified by site-directed mutagenesis have been performed, their exact catalytic mechanism remains controversial. This review attempts to summarize and to discuss the many available data. [less ▲]

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See detailKinetic Study of Interaction between Brl 42715, Beta-Lactamases, and D-Alanyl-D-Alanine Peptidases
Matagne, André ULg; Ledent, Philippe; Monnaie, Didier et al

in Antimicrobial Agents and Chemotherapy (1995), 39(1), 227-31

A detailed kinetic study of the interactions between BRL 42715, a beta-lactamase-inhibiting penem, and various beta-lactamases (EC 3.5.2.6) and D-alanyl-D-alanine peptidases (DD-peptidases, EC 3.4.16.4 ... [more ▼]

A detailed kinetic study of the interactions between BRL 42715, a beta-lactamase-inhibiting penem, and various beta-lactamases (EC 3.5.2.6) and D-alanyl-D-alanine peptidases (DD-peptidases, EC 3.4.16.4) is presented. The compound was a very efficient inactivator of all active-site serine beta-lactamases but was hydrolyzed by the class B, Zn(2+)-containing enzymes, with very different kcat values. Inactivation of the Streptomyces sp. strain R61 extracellular DD-peptidase was not observed, and the Actinomadura sp. strain R39 DD-peptidase exhibited a low level of sensitivity to the compound. [less ▲]

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See detailStreptomyces K15 active-site serine DD-transpeptidase: specificity profile for peptide, thiol ester and ester carbonyl donors and pathways of the transfer reactions.
Grandchamps, Jacqueline; Distèche, Martine ULg; Damblon, Christian ULg et al

in Biochemical Journal (1995), 307(Pt 2), 335-339

The Streptomyces K15 transferase is a penicillin-binding protein presumed to be involved in bacterial wall peptidoglycan crosslinking. It catalyses cleavage of the peptide, thiol ester or ester bond of ... [more ▼]

The Streptomyces K15 transferase is a penicillin-binding protein presumed to be involved in bacterial wall peptidoglycan crosslinking. It catalyses cleavage of the peptide, thiol ester or ester bond of carbonyl donors Z-R1-CONH-CHR2-COX-CHR3-COO- (where X is NH, S or O) and transfers the electrophilic group Z-R1-CONH-CHR2-CO to amino acceptors via an acyl-enzyme intermediate. Kinetic data suggest that the amino acceptor behaves as a simple alternative nucleophile at the level of the acyl-enzyme in the case of thiol ester and ester donors, and that it binds to the enzyme.carbonyl donor Michaelis complex and influences the rate of enzyme acylation by the carbonyl donor in the case of amide donors. Depending on the nature of the scissile bond, the enzyme has different requirements for substituents at positions R1, R2 and R3. [less ▲]

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See detailThe 3-D structure of a zinc metallo-beta-lactamase from Bacillus cereus reveals a new type of protein fold
Carfi, A.; Pares, S.; Duée, E. et al

in EMBO Journal (1995), 14(20), 4914-4921

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See detailTEM1 beta-lactamase structure solved by molecular replacement and refined structure of the S235A mutant.
Fonze, E.; Charlier, Paulette ULg; To'th, Y. et al

in Acta Crystallographica Section D-Biological Crystallography (1995), 51(Pt 5), 682-94

beta-Lactamases are bacterial enzymes which catalyse the hydrolysis of the beta-lactam ring of penicillins, cephalosporins and related compounds, thus inactivating these antibiotics. The crystal structure ... [more ▼]

beta-Lactamases are bacterial enzymes which catalyse the hydrolysis of the beta-lactam ring of penicillins, cephalosporins and related compounds, thus inactivating these antibiotics. The crystal structure of the TEM1 beta-lactamase has been determined at 1.9 A resolution by the molecular-replacement method, using the atomic coordinates of two homologous beta-lactamase refined structures which show about 36% strict identity in their amino-acid sequences and 1.96 A r.m.s. deviation between equivalent Calpha atoms. The TEM1 enzyme crystallizes in space group P2(1)2(1)2(1) and there is one molecule per asymmetric unit. The structure was refined by simulated annealing to an R-factor of 15.6% for 15 086 reflections with I >/= 2sigma(I) in the resolution range 5.0-1.9 A. The final crystallographic structure contains 263 amino-acid residues, one sulfate anion in the catalytic cleft and 135 water molecules per asymmetric unit. The folding is very similar to that of the other known class A beta-lactamases. It consists of two domains, the first is formed by a five-stranded beta-sheet covered by three alpha-helices on one face and one alpha-helix on the other, the second domain contains mainly alpha-helices. The catalytic cleft is located at the interface between the two domains. We also report the crystallographic study of the TEM S235A mutant. This mutation of an active-site residue specifically decreases the acylation rate of cephalosporins. This TEM S235A mutant crystallizes under the same conditions as the wild-type protein and its structure was refined at 2.0 A resolution with an R value of 17.6%. The major modification is the appearance of a water molecule near the mutated residue, which is incompatible with the OG 235 present in the wild-type enzyme, and causes very small perturbations in the interaction network in the active site. [less ▲]

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See detailThiolester substrates of DD-peptidases and beta-lactamases
Damblon, Christian ULg; Ledent, P.; Zhao, G. H. et al

in Letters In Peptide Science (1995), 2(3-4), 212-216

With peptide substrates, the penicillin-sensitive DD-peptidases exhibit a strict specificity for D-Ala-D-Xaa C-termini. Only glycine is tolerated as the C-terminal residue, but with a significantly ... [more ▼]

With peptide substrates, the penicillin-sensitive DD-peptidases exhibit a strict specificity for D-Ala-D-Xaa C-termini. Only glycine is tolerated as the C-terminal residue, but with a significantly decreased activity. These enzymes also hydrolyse various ester and thiolester analogues of their natural substrates. Some of the thiolesters whose C-terminal leaving group exhibited an L stereochemistry were significantly hydrolysed by some of the studied enzymes, particularly by the Actinomadura R39 DD-peptidase. By contrast, the strict specificity for a D residue in the penultimate position was fully retained. The same esters and thiolesters also behaved as substrates for beta-lactamases. In this case, thiolesters exhibiting L stereochemistry in the C-terminal position could also be hydrolysed, mainly by the class C and class D enzymes. But, more surprisingly, the class C Enterobacter cloacae P99 beta-lactamase also hydrolysed thiolesters containing an L residue in the penultimate position, sometimes more efficiently than the D isomer. [less ▲]

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See detailBreakdown of the stereospecificity of DD-peptidases and beta-lactamases with thiolester substrates.
Damblon, Christian ULg; Zhao, G. H.; Jamin, M. et al

in Biochemical Journal (1995), 309 ( Pt 2)

With peptide analogues of their natural substrates (the glycopeptide units of nascent peptidoglycan), the DD-peptidases exhibit a strict preference for D-Ala-D-Xaa C-termini. Gly is tolerated as the C ... [more ▼]

With peptide analogues of their natural substrates (the glycopeptide units of nascent peptidoglycan), the DD-peptidases exhibit a strict preference for D-Ala-D-Xaa C-termini. Gly is tolerated as the C-terminal residue, but with a significantly decreased activity. These enzymes were also known to hydrolyse various ester and thiolester analogues of their natural substrates. Some thiolesters with a C-terminal leaving group that exhibited L stereochemistry were significantly hydrolysed by some of the enzymes, particularly the Actinomadura R39 DD-peptidase, but the strict specificity for a D residue in the penultimate position was fully retained. These esters and thiolesters also behave as substrates for beta-lactamases. In this case, thiolesters exhibiting L stereochemistry in the ultimate position could also be hydrolysed, mainly by the class-C and class-D enzymes. However, more surprisingly, the class-C Enterobacter cloacae P99 beta-lactamase also hydrolysed thiolesters containing an L residue in the penultimate position, sometimes with a higher efficiency than the D isomer. [less ▲]

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See detailErratum for : primary structure of the streptomyces R61 extracellular DD-peptidase. 1. Cloning into Streptomyces lividans and nucleotide sequence of the gene
Duez, Colette ULg; Piron-Fraipont, C.; Joris, Bernard ULg et al

in European Journal of Biochemistry (1994), 224(3), 1079

This is the correction of the fig. 5 of Primary structure of the Streptomyces R61 extracellular DD-peptidase. 1. Cloning into Streptomyces Zividuns and nucleotide sequence of the gene, by C. Duez, C ... [more ▼]

This is the correction of the fig. 5 of Primary structure of the Streptomyces R61 extracellular DD-peptidase. 1. Cloning into Streptomyces Zividuns and nucleotide sequence of the gene, by C. Duez, C. Piron-Fraipont, B. Joris, J. Dusart, M. S. Urdea, J. A. Martial, J.-M. Frère and J.-M. Ghuysen. European Journal of Biochemistry Volume 162, Issue 3, pages 509–518, February 1987 [less ▲]

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