Unexpected influence of ionic strength on branched-pathway interactions between beta-lactamases and beta-halogenopenicillanates (original) (raw)
Related papers
Biochemical Journal, 1989
Ionic strength strongly influenced the turnover/inactivation ratio in the interaction between beta-halogenopenicillanates and some class A beta-lactamases. This suggested the stabilization of a highly charged intermediate by solvation. Those data could be interpreted on the basis of a reaction pathway where an episulphonium ion was transiently formed. The various mechanisms proposed for explaining the formation of the dihydrothiazine chromophore are discussed.
A study of the nucleophilic attack of the beta-lactamic bond of antibiotics in water solution
Journal of Molecular Structure: THEOCHEM, 2001
The nucleophilic attack of a series of 19 b-lactamic antibiotics (13 penicillins and six cephalosporins), as well as that of the clavulanic acid (CLA), by a hydroxylic anion, is considered in water solution and in gas phase. It is found that the tetrahedral intermediate formation does not occur spontaneously anymore in water solution, but the reaction has to overpass an energy barrier due to the desolvation of the reactants. The desolvation energy barriers, as well as the tetrahedral complex formation energy in water solution are calculated into the PM3 semi-empirical approach and the supermolecule model. In the same way, the energy barriers for the b-lactamic bond breaking and the ®nal product formation energies are determined. The results are compared with those obtained previously for the same molecules in the gas phase.
FEMS Microbiology Letters, 2000
The plasmid-mediated TEM-I and TEM-2 p-lactamases are the most commonly encountered among Gram-negative bacteria. They belong to molecular class A, and differ by one amino acid at position 39 : TEM-1 have a glutamine and TEM-2 a lysine. Kinetic parameters (& and I&) and catalytic efftciency (k,,JK,,,) of TEM-1 and TEM-2 P-lactamases are slightly, but significantly different. For all antibiotics except methicillin and cefazolin, the catalytic efficiency values of TEM-2 are clearly greater than that of TEM-1. Molecular modelling of TEM-2, when compared to that of TEM-1, showed an additional ionic bond between Lys-39 and Glu-281.
Journal of Enzyme Inhibition, 1999
The interaction between tazobactam and several chromosome-and plasmid-encoded (TEM, SHV, PSE types) class A and C p-lactamases was studied by spectrophotometry. Tazobactam behaved as a competitive inhibitor or inactivator able to restore in several cases the efficiency of piperacillin as a partner 8-lactam. A detailed kinetic analysis permitted measurement of the acylation efficiency for some cephalosporinases and broad-spectrum 8-lactamases; the presence of a turnover of acyl-enzyme complex was also evaluated.
Journal of the American Chemical Society, 2009
6-β-Halogenopenicillanates are powerful irreversible inhibitors of various β-lactamases and penicillin binding proteins. Upon acylation of these enzymes, the inhibitors are thought to undergo a structural rearrangement associated with the departure of the iodide and formation of a dihydrothiazine ring, but, to date, no structural evidence has proven this. 6-β-Iodopenicillanic (BIP) is here shown to be an active antibiotic against various bacterial strains and an effective inhibitor of the class A β-lactamase of Bacillus subtilis BS3 (BS3) and the D,D-peptidase of Actinomadura R39 (R39). Crystals of BS3 and of R39 were soaked with a solution of BIP and their structures solved at 1.65 Å and 2.2 Å, respectively. The β-lactam and the thiazolidine rings of BIP are indeed found to be fused into a dihydrothiazine ring that can adopt two stable conformations at these active sites. The rearranged BIP is observed in one conformation in the BS3 active site and in two monomers of the asymmetric unit of R39, and is observed in the other conformation in the other two monomers of the asymmetric unit of R39. The BS3 structure reveals a new mode of carboxylate interaction with a class A β-lactamase active site that should be of interest in future inhibitor design.
Drifted catalytic properties of β-lactamases due to unconstrained use of antibiotics
Context: Antibiotic resistance is an old problem with new face as the rate of infections due to multidrug resistant bacteria is increasing everyday and the number of new antibiotics to overwhelm the problem is becoming smaller. Major mechanism beneath this growing resistance is concomitant with the changes in β-lactamases catalytic activity and its functional enhancement. Objectives: In β-lactamases secreting clinical isolates at least 10% are extended-spectrum β-lactamases (ESBL) that are not even treatable with β-lactamases inhibitor like clavulanic acids. This implies that the catalytic domains of β-lactamases have been mutated towards higher pathogenicity. The aim of the present study is to define the changes in β-lactamases catalytic efficiency against β-lactam antibiotics and its inhibitors. Materials and Methods: In this research work we have used multiple drug resistant (MDR) strains from surgical site of infections. A rapid method was used for specific detection of bacterial β-lactamases that uses β-lactam antibiotics as substrates. In this, the end products (open beta-lactam ring forms) generated after separately incubating substrates with β-lactamases producing strains. Those end products of antibiotics were highly fluorescent after specific treatment and could be analyzed visually under long-wave UV lamp for efficiency. Results: β-lactamases secreting strains are variably capable of defending β-lactam antibiotics. Interestingly, one of the E. coli strain secretes ESBL, this means that the strain is resistant against clavulanic acid. However, the most fascinating fact of the finding is that ideally the β-lactamases supposed to hydrolyze Penicillin by default but in our isolates, β-lactamases are not able to hydrolyze penicillin instead they hydrolyze amoxicillin, a derivative which replaced clinical use of penicillin. In addition to that we have identified the presence of New Delhi Metalo-betalactamase in one of the clinical isolates. Conclusion: Rate of evolution in microbes is very high. Thus we presume that some of the amino acids in the functional domain of β-lactamases have been changed respective to extinct use of penicillin whereas it is effective against clinically used other beta lactam antibiotics.
Kinetic interactions of tazobactam with beta-lactamases from all major structural classes
Antimicrobial Agents and Chemotherapy, 1993
Tazobactam was shown to be a potent inhibitor of group 1, 2a, 2b, and 2b' beta-lactamases. Extended kinetic studies with class A and C serine beta-lactamases showed that the PC1, TEM-2, and P99 enzymes all were reversibly inhibited prior to inactivation of the enzymes. The CcrA metallo-beta-lactamase was less well inhibited, with a 50% inhibitory concentration at least 3 orders of magnitude less favorable than those for most serine beta-lactamases. The numbers of hydrolytic turnovers of tazobactam before inactivation were 2 for PC1, 125 for TEM-2, 50 for P99, and 4,000 for the CcrA enzyme. In spectral studies, transient intermediates were formed after reaction of tazobactam with the PC1, TEM-2, and CcrA beta-lactamases, corresponding to enzyme-associated intermediates responsible for hydrolysis of tazobactam. Chromophores absorbing at 270 nm (CcrA) and 288 nm (TEM-2 and PC1) were observed for these reaction intermediates. The P99 cephalosporinase formed a stable complex with a U...