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Beta-Lactam Ring

The Experts below are selected from a list of 195 Experts worldwide ranked by ideXlab platform

J Heesemann – 1st expert on this subject based on the ideXlab platform

  • [Mechanisms of resistance to Beta-Lactam antibiotics].
    Infection, 1993
    Co-Authors: J Heesemann

    Abstract:

    Beta-Lactam antibiotics share the structural feature of a Beta-Lactam Ring. This feature is responsible for inhibition of bacterial cell wall synthesis. The target molecules are peptidoglycan cross-linking enzymes (e.g. transpeptidases and carboxypeptidases) which can bind Beta-Lactam antibiotics (penicillin binding proteins, PBP). Bacterial cell death is initiated by Beta-Lactam antibiotic-triggered release of autolytic enzymes. In contrast to gram-positive bacteria (absence of an outer membrane) the antibiotic has to penetrate through porins of the outer membrane of gram-negative bacteria before touching PBP’s. Bacterial resistance to Beta-Lactam antibiotics includes modification of porins (permeability barrier) and of targets (low affinity of PBP’s for the drug), production of inactivating enzymes (Beta-Lactamases) and inhibition of release of autolytic enzymes. Moreover, bacteria have developed sophisticated genetic mechanisms to adapt to treatments with novel Beta-Lactam antibiotics. To allow successful antibiotic treatment of bacterial infection in the future, knowledge about antibiotic resistance mechanisms is required.

M Menendez – 2nd expert on this subject based on the ideXlab platform

  • Interaction of Beta-Lactamases I and II from Bacillus cereus with semisynthetic cephamycins. Kinetic studies.
    The Biochemical journal, 1991
    Co-Authors: J Martin Villacorta, P Arriaga, J Laynez, M Menendez

    Abstract:

    The influence of C-6 alpha- or C-7 alpha-methoxylation of the Beta-Lactam Ring in the catalytic action of class A and B Beta-Lactamases has been investigated. For this purpose the kinetic behaviour of Beta-Lactamases I (class A) and II (class B) from Bacillus cereus was analysed by using several cephamycins, moxalactam, temocillin and related antibiotics. These compounds behaved as poor substrates for Beta-Lactamase II, with high Km values and very low catalytic efficiencies. In the case of Beta-Lactamase I, the substitution of a methoxy group for a H atom at C-7 alpha or C-6 alpha decreased the affinity of the substrates for the enzyme. Furthermore, the acylation of cephamycins was completely blocked, whereas that of penicillins was slowed down by a factor of 10(4)-10(5), acylation being the rate-determining step of the process.

  • Interaction of β-lactamases I and II from Bacillus cereus with semisynthetic cephamycins. Kinetic studies
    Biochemical Journal, 1991
    Co-Authors: J Martin Villacorta, J Laynez, P Arriaga, M Menendez

    Abstract:

    The influence of C-6 alpha- or C-7 alpha-methoxylation of the Beta-Lactam Ring in the catalytic action of class A and B Beta-Lactamases has been investigated. For this purpose the kinetic behaviour of Beta-Lactamases I (class A) and II (class B) from Bacillus cereus was analysed by using several cephamycins, moxalactam, temocillin and related antibiotics. These compounds behaved as poor substrates for Beta-Lactamase II, with high Km values and very low catalytic efficiencies. In the case of Beta-Lactamase I, the substitution of a methoxy group for a H atom at C-7 alpha or C-6 alpha decreased the affinity of the substrates for the enzyme. Furthermore, the acylation of cephamycins was completely blocked, whereas that of penicillins was slowed down by a factor of 10(4)-10(5), acylation being the rate-determining step of the process.

Timothy G. Palzkill – 3rd expert on this subject based on the ideXlab platform

  • Molecular analysis of Beta-Lactamase structure and function
    International Journal of Medical Microbiology, 2002
    Co-Authors: Fahd K. Majiduddin, Isabel C. Materon, Timothy G. Palzkill

    Abstract:

    The extensive and sometimes irresponsible use of Beta-Lactam antibiotics in clinical and agricultural settings has contributed to the emergence and widespread dissemination of antibiotic-resistant bacteria. Bacteria have evolved three strategies to escape the activity of Beta-Lactam antibiotics: 1) alteration of the target site (e.g. penicillin-binding protein (PBPs), 2) reduction of drug permeation across the bacterial membrane (e.g. efflux pumps) and 3) production of Beta-Lactamase enzymes. The Beta-Lactamase enzymes inactivate Beta-Lactam antibiotics by hydrolyzing the peptide bond of the characteristic four-membered Beta-Lactam Ring rendeRing the antibiotic ineffective. The inactivation of the antibiotic provides resistance to the bacterium. Currently, there are over 300 Beta-Lactamase enzymes described for which numerous kinetic, structural, computational and mutagenesis studies have been performed. In this review, we discuss the recent work performed on the four different classes (A, B, C, and D) of Beta-Lactamases. These investigative advances further expand our knowledge about these complex enzymes, and hopefully, will provide us with additional tools to develop new inhibitors and antibiotics based on structural and rational designs.