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Li A, Yan C, Zhang L, Liu S, Feng C, Zhang L, Dong F, Sheng X, Wang L, Zhang Y, Lu J, Xu J, Zheng L, Bao Q, Cheng C, Huang D. Characterization and identification of a novel chromosomal class C β-lactamase, LAQ-1, and comparative genomic analysis of a multidrug resistance plasmid in Lelliottia amnigena P13. Front Microbiol 2022; 13:990736. [PMID: 36504772 PMCID: PMC9727190 DOI: 10.3389/fmicb.2022.990736] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2022] [Accepted: 11/08/2022] [Indexed: 11/24/2022] Open
Abstract
Introduction Lelliottia amnigena, a bacterium usually isolated from natural environments, may cause human infections and has been suggested to be naturally resistant to second- and third-generation cephalosporins. Methods In this study, we determined the whole-genome sequence of an isolate, L. Amnigena P13, isolated from animal farm sewage. On the basis of genome sequence analysis, susceptibility testing, molecular cloning, and enzyme kinetic parameter analysis, we identified a novel chromosome-encoded AmpC β-lactamase, LAQ-1. Results and Discussion bla LAQ-1 is resistant to penicillin G, ampicillin, and several first- to fourth-generation cephalosporins, such as cefazolin, cefoxitin and cefepime. The MIC levels of some β-lactams, such as cefoxitin, cefepime, aztreonam and cefazolin, for the recombinant clone (pUCP24-bla LAQ-1/DH5α) increased by approximately 4- to 64-fold compared with those of the control strain (pUCP24/DH5α). The kinetic properties of LAQ-1, with the highest catalytic activity observed toward piperacillin, were basically the same as those of typical class C β-lactamases, and avibactam had a strong inhibitory effect on its hydrolytic activity. The genetic background of bla LAQ-1 was relatively conserved, and no mobile genetic element (MGE) was found around it. The plasmid pP13-67 of L. amnigena P13 harbored 12 resistance genes [qnrS1, aph(6)-Id, aadA2, sul1, sul2, bla TEM-1, qacEΔ1, dfrA12, tetA and floR] related to different mobile genetic elements within an ~22 kb multidrug resistance region. The multidrug resistance region shared the highest nucleotide sequence similarities with those of the chromosomes or plasmids of different bacterial species, indicating the possibility of horizontal transfer of these resistance genes among different bacterial species.
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Affiliation(s)
- Anqi Li
- School of Medicine, Lishui University, Lishui, China,Key Laboratory of Medical Genetics of Zhejiang Province, Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, China
| | - Chunxia Yan
- Medical Molecular Biology Laboratory, School of Medicine, Jinhua Polytechnic, Jinhua, China
| | - Lei Zhang
- Key Laboratory of Medical Genetics of Zhejiang Province, Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, China
| | - Shuang Liu
- Key Laboratory of Medical Genetics of Zhejiang Province, Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, China
| | - Chunlin Feng
- Key Laboratory of Medical Genetics of Zhejiang Province, Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, China
| | | | - Fubo Dong
- The People’s Hospital of Yuhuan, Yuhuan, China
| | - Xiusheng Sheng
- Medical Molecular Biology Laboratory, School of Medicine, Jinhua Polytechnic, Jinhua, China
| | - Lan Wang
- Medical Molecular Biology Laboratory, School of Medicine, Jinhua Polytechnic, Jinhua, China
| | - Yanfang Zhang
- Medical Molecular Biology Laboratory, School of Medicine, Jinhua Polytechnic, Jinhua, China
| | - Junwan Lu
- Medical Molecular Biology Laboratory, School of Medicine, Jinhua Polytechnic, Jinhua, China
| | - Jiefeng Xu
- Medical Molecular Biology Laboratory, School of Medicine, Jinhua Polytechnic, Jinhua, China
| | - Lin Zheng
- Department of Clinical Laboratory, Hospital of Ningbo University School of Medicine, Ningbo, Zhejiang, China
| | - Qiyu Bao
- Key Laboratory of Medical Genetics of Zhejiang Province, Key Laboratory of Laboratory Medicine, Ministry of Education of China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, China,Medical Molecular Biology Laboratory, School of Medicine, Jinhua Polytechnic, Jinhua, China
| | - Cong Cheng
- School of Medicine, Lishui University, Lishui, China,*Correspondence: Cong Cheng,
| | - Dawei Huang
- The People’s Hospital of Yuhuan, Yuhuan, China,Dawei Huang,
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Abstract
Class C β-lactamases or cephalosporinases can be classified into two functional groups (1, 1e) with considerable molecular variability (≤20% sequence identity). These enzymes are mostly encoded by chromosomal and inducible genes and are widespread among bacteria, including Proteobacteria in particular. Molecular identification is based principally on three catalytic motifs (64SXSK, 150YXN, 315KTG), but more than 70 conserved amino-acid residues (≥90%) have been identified, many close to these catalytic motifs. Nevertheless, the identification of a tiny, phylogenetically distant cluster (including enzymes from the genera Legionella, Bradyrhizobium, and Parachlamydia) has raised questions about the possible existence of a C2 subclass of β-lactamases, previously identified as serine hydrolases. In a context of the clinical emergence of extended-spectrum AmpC β-lactamases (ESACs), the genetic modifications observed in vivo and in vitro (point mutations, insertions, or deletions) during the evolution of these enzymes have mostly involved the Ω- and H-10/R2-loops, which vary considerably between genera, and, in some cases, the conserved triplet 150YXN. Furthermore, the conserved deletion of several amino-acid residues in opportunistic pathogenic species of Acinetobacter, such as A. baumannii, A. calcoaceticus, A. pittii and A. nosocomialis (deletion of residues 304-306), and in Hafnia alvei and H. paralvei (deletion of residues 289-290), provides support for the notion of natural ESACs. The emergence of higher levels of resistance to β-lactams, including carbapenems, and to inhibitors such as avibactam is a reality, as the enzymes responsible are subject to complex regulation encompassing several other genes (ampR, ampD, ampG, etc.). Combinations of resistance mechanisms may therefore be at work, including overproduction or change in permeability, with the loss of porins and/or activation of efflux systems.
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Yadav TC, Agarwal V, Srivastava AK, Raghuwanshi N, Varadwaj P, Prasad R, Pruthi V. Insight into Structure-Function Relationships of β-Lactamase and BLIPs Interface Plasticity using Protein-Protein Interactions. Curr Pharm Des 2020; 25:3378-3389. [PMID: 31544712 DOI: 10.2174/1381612825666190911154650] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 09/05/2019] [Indexed: 11/22/2022]
Abstract
BACKGROUND Mostly BLIPs are identified in soil bacteria Streptomyces and originally isolated from Streptomyces clavuligerus and can be utilized as a model system for biophysical, structural, mutagenic and computational studies. BLIP possess homology with two proteins viz., BLIP-I (Streptomyces exofoliatus) and BLP (beta-lactamase inhibitory protein like protein from S. clavuligerus). BLIP consists of 165 amino acid, possessing two homologues domains comprising helix-loop-helix motif packed against four stranded beta-sheet resulting into solvent exposed concave surface with extended four stranded beta-sheet. BLIP-I is a 157 amino acid long protein obtained from S. exofoliatus having 37% sequence identity to BLIP and inhibits beta-lactamase. METHODS This review is intended to briefly illustrate the beta-lactamase inhibitory activity of BLIP via proteinprotein interaction and aims to open up a new avenue to combat antimicrobial resistance using peptide based inhibition. RESULTS D49A mutation in BLIP-I results in a decrease in affinity for TEM-1 from 0.5 nM to 10 nM (Ki). It is capable of inhibiting TEM-1 and bactopenemase and differs from BLIP only in modulating cell wall synthesis enzyme. Whereas, BLP is a 154 amino acid long protein isolated from S. clavuligerus via DNA sequencing analysis of Cephamycin-Clavulanate gene bunch. It shares 32% sequence similarity with BLIP and 42% with BLIP-I. Its biological function is unclear and lacks beta-lactamase inhibitory activity. CONCLUSION Protein-protein interactions mediate a significant role in regulation and modulation of cellular developments and processes. Specific biological markers and geometric characteristics are manifested by active site binding clefts of protein surfaces which determines the specificity and affinity for their targets. TEM1.BLIP is a classical model to study protein-protein interaction. β-Lactamase inhibitory proteins (BLIPs) interacts and inhibits various β-lactamases with extensive range of affinities.
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Affiliation(s)
- Tara C Yadav
- Department of Biotechnology, Indian Institute of Technology, Roorkee-247667, Uttarakhand, India
| | - Vidhu Agarwal
- Department of Bioinformatics, Indian Institute of Information Technology, Allahabad 211015, India
| | - Amit K Srivastava
- Department of Biotechnology, Indian Institute of Technology, Roorkee-247667, Uttarakhand, India
| | - Navdeep Raghuwanshi
- Vaccine Formulation & Research Center, Gennova (Emcure) Biopharmaceuticals Limited, Pune - 11057, Maharashtra, India
| | - Pritish Varadwaj
- Department of Bioinformatics, Indian Institute of Information Technology, Allahabad 211015, India
| | - Ramasare Prasad
- Department of Biotechnology, Indian Institute of Technology, Roorkee-247667, Uttarakhand, India
| | - Vikas Pruthi
- Department of Biotechnology, Indian Institute of Technology, Roorkee-247667, Uttarakhand, India
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Tackling the Antibiotic Resistance Caused by Class A β-Lactamases through the Use of β-Lactamase Inhibitory Protein. Int J Mol Sci 2018; 19:ijms19082222. [PMID: 30061509 PMCID: PMC6121496 DOI: 10.3390/ijms19082222] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2018] [Revised: 07/23/2018] [Accepted: 07/25/2018] [Indexed: 12/27/2022] Open
Abstract
β-Lactams are the most widely used and effective antibiotics for the treatment of infectious diseases. Unfortunately, bacteria have developed several mechanisms to combat these therapeutic agents. One of the major resistance mechanisms involves the production of β-lactamase that hydrolyzes the β-lactam ring thereby inactivating the drug. To overcome this threat, the small molecule β-lactamase inhibitors (e.g., clavulanic acid, sulbactam and tazobactam) have been used in combination with β-lactams for treatment. However, the bacterial resistance to this kind of combination therapy has evolved recently. Therefore, multiple attempts have been made to discover and develop novel broad-spectrum β-lactamase inhibitors that sufficiently work against β-lactamase producing bacteria. β-lactamase inhibitory proteins (BLIPs) (e.g., BLIP, BLIP-I and BLIP-II) are potential inhibitors that have been found from soil bacterium Streptomyces spp. BLIPs bind and inhibit a wide range of class A β-lactamases from a diverse set of Gram-positive and Gram-negative bacteria, including TEM-1, PC1, SME-1, SHV-1 and KPC-2. To the best of our knowledge, this article represents the first systematic review on β-lactamase inhibitors with a particular focus on BLIPs and their inherent properties that favorably position them as a source of biologically-inspired drugs to combat antimicrobial resistance. Furthermore, an extensive compilation of binding data from β-lactamase–BLIP interaction studies is presented herein. Such information help to provide key insights into the origin of interaction that may be useful for rationally guiding future drug design efforts.
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Juan C, Torrens G, González-Nicolau M, Oliver A. Diversity and regulation of intrinsic β-lactamases from non-fermenting and other Gram-negative opportunistic pathogens. FEMS Microbiol Rev 2018; 41:781-815. [PMID: 29029112 DOI: 10.1093/femsre/fux043] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Accepted: 08/18/2017] [Indexed: 01/22/2023] Open
Abstract
This review deeply addresses for the first time the diversity, regulation and mechanisms leading to mutational overexpression of intrinsic β-lactamases from non-fermenting and other non-Enterobacteriaceae Gram-negative opportunistic pathogens. After a general overview of the intrinsic β-lactamases described so far in these microorganisms, including circa. 60 species and 100 different enzymes, we review the wide array of regulatory pathways of these β-lactamases. They include diverse LysR-type regulators, which control the expression of β-lactamases from relevant nosocomial pathogens such as Pseudomonas aeruginosa or Stenothrophomonas maltophilia or two-component regulators, with special relevance in Aeromonas spp., along with other pathways. Likewise, the multiple mutational mechanisms leading to β-lactamase overexpression and β-lactam resistance development, including AmpD (N-acetyl-muramyl-L-alanine amidase), DacB (PBP4), MrcA (PPBP1A) and other PBPs, BlrAB (two-component regulator) or several lytic transglycosylases among others, are also described. Moreover, we address the growing evidence of a major interplay between β-lactamase regulation, peptidoglycan metabolism and virulence. Finally, we analyse recent works showing that blocking of peptidoglycan recycling (such as inhibition of NagZ or AmpG) might be useful to prevent and revert β-lactam resistance. Altogether, the provided information and the identified gaps should be valuable for guiding future strategies for combating multidrug-resistant Gram-negative pathogens.
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Affiliation(s)
- Carlos Juan
- Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases-Instituto de Investigación Sanitaria de Baleares (IdISBa), 07120 Palma, Illes Balears, Spain
| | - Gabriel Torrens
- Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases-Instituto de Investigación Sanitaria de Baleares (IdISBa), 07120 Palma, Illes Balears, Spain
| | - Mar González-Nicolau
- Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases-Instituto de Investigación Sanitaria de Baleares (IdISBa), 07120 Palma, Illes Balears, Spain
| | - Antonio Oliver
- Servicio de Microbiología and Unidad de Investigación, Hospital Son Espases-Instituto de Investigación Sanitaria de Baleares (IdISBa), 07120 Palma, Illes Balears, Spain
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ESBL-producing Escherichia coli
and Its Rapid Rise among Healthy People. Food Saf (Tokyo) 2017; 5:122-150. [PMID: 32231938 DOI: 10.14252/foodsafetyfscj.2017011] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 12/11/2017] [Indexed: 02/06/2023] Open
Abstract
Since around the 2000s, Escherichia coli (E. coli) resistant to both oxyimino-cephalosporins and fluoroquinolones has remarkably increased worldwide in clinical settings. The kind of E. coli is also identified in patients suffering from community-onset infectious diseases such as urinary tract infections. Moreover, recoveries of multi-drug resistant E. coli from the feces of healthy people have been increasingly documented in recent years, although the actual state remains uncertain. These E. coli isolates usually produce extended-spectrum β-lactamase (ESBL), as well as acquisition of amino acid substitutions in the quinolone-resistance determining regions (QRDRs) of GyrA and/or ParC, together with plasmid-mediated quinolone resistance determinants such as Qnr, AAC(6')-Ib-cr, and QepA. The actual state of ESBL-producing E. coli in hospitalized patients has been carefully investigated in many countries, while that in healthy people still remains uncertain, although high fecal carriage rates of ESBL producers in healthy people have been reported especially in Asian and South American countries. The issues regarding the ESBL producers have become very complicated and chaotic due to rapid increase of both ESBL variants and plasmids mediating ESBL genes, together with the emergence of various "epidemic strains" or "international clones" of E. coli and Klebsiella pneumoniae harboring transferable-plasmids carrying multiple antimicrobial resistance genes. Thus, the current state of ESBL producers outside hospital settings was overviewed together with the relation among those recovered from livestock, foods, pets, environments and wildlife from the viewpoint of molecular epidemiology. This mini review may contribute to better understanding about ESBL producers among people who are not familiar with the antimicrobial resistance (AMR) threatening rising globally.
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Hsieh WS, Wang NY, Feng JA, Weng LC, Wu HH. Identification of DHA-23, a novel plasmid-mediated and inducible AmpC beta-lactamase from Enterobacteriaceae in Northern Taiwan. Front Microbiol 2015; 6:436. [PMID: 25999942 PMCID: PMC4422083 DOI: 10.3389/fmicb.2015.00436] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 04/22/2015] [Indexed: 12/04/2022] Open
Abstract
Objectives: AmpC β-lactamases are classified as Amber Class C and Bush Group 1. AmpC β-lactamases can hydrolyze broad and extended-spectrum cephalosporins, and are not inhibited by β-lactamase inhibitors such as clavulanic acid. This study was conducted to identify DHA-23, a novel plasmid-mediated and inducible AmpC β-lactamase obtained from Enterobacteriaceae. Methods: A total of 210 carbapenem-resistant Enterobacteriaceae isolates were collected from a medical center (comprising two branches) in Northern Taiwan during 2009–2012. AmpC β-lactamase genes were analyzed through a polymerase chain reaction using plasmid DNA templates and gene sequencing. The genetic relationships of the isolates were typed using pulsed-field gel electrophoresis following the digestion of intact genomic DNA by using XbaI. Results: Three enterobacterial isolates (one Escherichia coli and two Klebsiella pneumoniae) were obtained from three hospitalized patients. All three isolates were resistant or intermediately susceptible to all β-lactams, and exhibited reduced susceptibility to carbapenems. These three isolates expressed a novel AmpC β-lactamase, designated DHA-23, approved by the curators of the Lahey website. DHA-23 differs from DHA-1 and DHA-6 by one amino acid substitution (Ser245Ala), exhibiting three amino acid changes compared with DHA-7 and DHA-Morganella morganii; three amino acid changes compared with DHA-3; four amino acid changes compared with DHA-5; and eight amino acid changes compared with DHA-2 (>97% identity). This AmpC β-lactamase is inducible using a system involving ampR. Conclusion: This is the first report to address DHA-23, a novel AmpC β-lactamase. DHA-type β-lactamases are continuous threat in Taiwan.
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Affiliation(s)
- Wen-Shyang Hsieh
- Department of Laboratory Medicine, Taipei Medical University - Shuang Ho Hospital, New Taipei City Taiwan ; School of Medical Laboratory Science and Biotechnology, Taipei Medical University, Taipei Taiwan ; Graduate Institute of Biomedical Informatics, Taipei Medical University, Taipei Taiwan
| | - Nai-Yu Wang
- Department of Medical Research, Mackay Memorial Hospital, New Taipei City Taiwan
| | - Jou-An Feng
- Department of Medical Research, Mackay Memorial Hospital, New Taipei City Taiwan
| | - Li-Chuan Weng
- Department of Medical Research, Mackay Memorial Hospital, New Taipei City Taiwan
| | - Hsueh-Hsia Wu
- School of Medical Laboratory Science and Biotechnology, Taipei Medical University, Taipei Taiwan ; Department of Laboratory Medicine, Taipei Medical University Hospital, Taipei Taiwan
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8
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Drawz SM, Taracila M, Caselli E, Prati F, Bonomo RA. Exploring sequence requirements for C₃/C₄ carboxylate recognition in the Pseudomonas aeruginosa cephalosporinase: Insights into plasticity of the AmpC β-lactamase. Protein Sci 2011; 20:941-58. [PMID: 21404358 DOI: 10.1002/pro.612] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Revised: 02/11/2011] [Accepted: 02/14/2011] [Indexed: 11/06/2022]
Abstract
In Pseudomonas aeruginosa, the chromosomally encoded class C cephalosporinase (AmpC β-lactamase) is often responsible for high-level resistance to β-lactam antibiotics. Despite years of study of these important β-lactamases, knowledge regarding how amino acid sequence dictates function of the AmpC Pseudomonas-derived cephalosporinase (PDC) remains scarce. Insights into structure-function relationships are crucial to the design of both β-lactams and high-affinity inhibitors. In order to understand how PDC recognizes the C₃/C₄ carboxylate of β-lactams, we first examined a molecular model of a P. aeruginosa AmpC β-lactamase, PDC-3, in complex with a boronate inhibitor that possesses a side chain that mimics the thiazolidine/dihydrothiazine ring and the C₃/C₄ carboxylate characteristic of β-lactam substrates. We next tested the hypothesis generated by our model, i.e. that more than one amino acid residue is involved in recognition of the C₃/C₄ β-lactam carboxylate, and engineered alanine variants at three putative carboxylate binding amino acids. Antimicrobial susceptibility testing showed that the PDC-3 β-lactamase maintains a high level of activity despite the substitution of C₃/C₄ β-lactam carboxylate recognition residues. Enzyme kinetics were determined for a panel of nine penicillin and cephalosporin analog boronates synthesized as active site probes of the PDC-3 enzyme and the Arg349Ala variant. Our examination of the PDC-3 active site revealed that more than one residue could serve to interact with the C₃/C₄ carboxylate of the β-lactam. This functional versatility has implications for novel drug design, protein evolution, and resistance profile of this enzyme.
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Affiliation(s)
- Sarah M Drawz
- Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, OH, USA
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Abstract
SUMMARY AmpC beta-lactamases are clinically important cephalosporinases encoded on the chromosomes of many of the Enterobacteriaceae and a few other organisms, where they mediate resistance to cephalothin, cefazolin, cefoxitin, most penicillins, and beta-lactamase inhibitor-beta-lactam combinations. In many bacteria, AmpC enzymes are inducible and can be expressed at high levels by mutation. Overexpression confers resistance to broad-spectrum cephalosporins including cefotaxime, ceftazidime, and ceftriaxone and is a problem especially in infections due to Enterobacter aerogenes and Enterobacter cloacae, where an isolate initially susceptible to these agents may become resistant upon therapy. Transmissible plasmids have acquired genes for AmpC enzymes, which consequently can now appear in bacteria lacking or poorly expressing a chromosomal bla(AmpC) gene, such as Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis. Resistance due to plasmid-mediated AmpC enzymes is less common than extended-spectrum beta-lactamase production in most parts of the world but may be both harder to detect and broader in spectrum. AmpC enzymes encoded by both chromosomal and plasmid genes are also evolving to hydrolyze broad-spectrum cephalosporins more efficiently. Techniques to identify AmpC beta-lactamase-producing isolates are available but are still evolving and are not yet optimized for the clinical laboratory, which probably now underestimates this resistance mechanism. Carbapenems can usually be used to treat infections due to AmpC-producing bacteria, but carbapenem resistance can arise in some organisms by mutations that reduce influx (outer membrane porin loss) or enhance efflux (efflux pump activation).
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Bush K, Jacoby GA, Medeiros AA. A functional classification scheme for beta-lactamases and its correlation with molecular structure. Antimicrob Agents Chemother 1995; 39:1211-33. [PMID: 7574506 PMCID: PMC162717 DOI: 10.1128/aac.39.6.1211] [Citation(s) in RCA: 1553] [Impact Index Per Article: 53.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Affiliation(s)
- K Bush
- American Cyanamid Company, Lederle Laboratories, Pearl River, New York 10965, USA
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11
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Matagne A, Frère JM. Contribution of mutant analysis to the understanding of enzyme catalysis: the case of class A beta-lactamases. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1246:109-27. [PMID: 7819278 DOI: 10.1016/0167-4838(94)00177-i] [Citation(s) in RCA: 92] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
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.
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Affiliation(s)
- A Matagne
- Laboratoire d'Enzymologie et Centre d'Ingénierie des Protéines, Université de Liège, Belgium
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12
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Horii T, Arakawa Y, Ohta M, Sugiyama T, Wacharotayankun R, Ito H, Kato N. Characterization of a plasmid-borne and constitutively expressed blaMOX-1 gene encoding AmpC-type beta-lactamase. Gene 1994; 139:93-8. [PMID: 8112596 DOI: 10.1016/0378-1119(94)90529-0] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A 1954-bp DNA fragment containing the blaMOX-1 gene, identified on a large resident plasmid (pRMOX-1) of Klebsiella pneumoniae NU2936, was sequenced and an open reading frame (ORF) coding for a 390-amino-acid (aa) MOX-1 was found. The total deduced aa sequence of MOX-1 shared considerable homology with that of AmpC-type class C beta-lactamases of Gram- bacteria, especially of Pseudomonas aeruginosa PAO1 [51.3%; 63.8% at the nucleotide (nt) level]. However, the regulatory gene ampR and a 38-bp AmpR-binding region were not present upstream from blaMOX-1, although the expression of P. aeruginosa ampC is directly regulated by AmpR. Possible -35 and -10 regions, a Shine-Dalgarno (SD) sequence and terminators were identified which are peculiar to blaMOX-1. On the other hand, a sequence highly homologous (91.6%) to the region upstream from dhfrX in the In7 integron carried by plasmid pDGO100 was found upstream from blaMOX-1 at nt 1 to 488. No significant difference was detected between the promoter activities of blaMOX-1 in ampD- and ampD+ strains of Enterobacter cloacae, as measured by the chloramphenicol acetyltransferase (CAT) assay. These results clearly show that blaMOX-1 belongs to the group of ampC-related bla genes and that it is expressed constitutively, independently of transcriptional regulators such as AmpR, AmpG and AmpD. Homology analysis among AmpC enzymes or ampC genes implied that integration of the chromosomal ampC gene into a large resident plasmid, followed by transconjugation, was involved in the evolution of blaMOX-1.
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Affiliation(s)
- T Horii
- Department of Bacteriology, Nagoya University School of Medicine, Japan
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Abstract
The hydrolysis time courses of 22 beta-lactam antibiotics by the class D OXA2 beta-lactamase were studied. Among these, only three appeared to correspond to the integrated Henri-Michaelis equation. 'Burst' kinetics, implying branched pathways, were observed with most penicillins, cephalosporins and with flomoxef and imipenem. Kinetic parameters characteristic of the different phases of the hydrolysis were determined for some substrates. Mechanisms generally accepted to explain such reversible partial inactivations involving branches at either the free enzyme or the acyl-enzyme were inadequate to explain the enzyme behaviour. The hydrolysis of imipenem was characterized by the occurrence of two 'bursts', and that of nitrocefin by a partial substrate-induced inactivation complicated by a competitive inhibition by the hydrolysis product.
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Affiliation(s)
- P Ledent
- Laboratoire d'Enzymologie, Université de Liège, Sart-Tilman, Belgium
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14
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Lodge JM, Minchin SD, Piddock LJ, Busby SJ. Cloning, sequencing and analysis of the structural gene and regulatory region of the Pseudomonas aeruginosa chromosomal ampC beta-lactamase. Biochem J 1990; 272:627-31. [PMID: 2125210 PMCID: PMC1149754 DOI: 10.1042/bj2720627] [Citation(s) in RCA: 106] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The chromosomal gene from Pseudomonas aeruginosa encoding beta-lactamase has been cloned, and the sequence determined and compared with corresponding sequences of beta-lactamases from members of the enterobacteriaceae. Upstream of the beta-lactamase gene is an open reading frame which we postulate encodes a regulatory protein, AmpR. We identified a helix-turn-helix region in AmpR and a putative AmpR-binding site.
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Affiliation(s)
- J M Lodge
- School of Biochemistry, University of Birmingham, U.K
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15
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Tsukamoto K, Tachibana K, Yamazaki N, Ishii Y, Ujiie K, Nishida N, Sawai T. Role of lysine-67 in the active site of class C beta-lactamase from Citrobacter freundii GN346. EUROPEAN JOURNAL OF BIOCHEMISTRY 1990; 188:15-22. [PMID: 1969344 DOI: 10.1111/j.1432-1033.1990.tb15365.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Citrobacter freundii GN346 produces a class C beta-lactamase exhibiting the substrate profile of a typical cephalosporinase. The structural and promoter regions of the cephalosporinase gene, comprising 1408 nucleotides, were completely sequenced. The amino acid sequence of the mature enzyme, comprising 361 amino acids, and its molecular mass, 39,878 Da, were determined. The active site was confirmed to be Ser-64. The amino acid sequence of the enzyme differs from that of the cephalosporinase of C. freundii OS60 by nine residues. The nucleotide sequence of the promoter region suggests a possible attenuator structure. Lys-67, one of the most conserved residues found in class A and C beta-lactamases and penicillin-binding proteins, was converted into arginine, threonine or glutamic acid through site-directed mutagenesis. The Glu-67 enzyme had lost the catalytic activity and the Thr-67 enzyme only showed a trace of activity. The Arg-67 enzyme, which retained a significant amount of the activity, was purified. The Km values of the Arg-67 enzyme for cephalothin, cephaloridine and benzylpenicillin are 13-19 times those of the wild-type enzyme; the kcat values for the three substrates are 37%, 3%, and 36% those of the wild-type enzyme, respectively.
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Affiliation(s)
- K Tsukamoto
- Division of Microbial Chemistry, Faculty of Pharmaceutical Sciences, Chiba University, Japan
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16
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Bush K. Classification of beta-lactamases: groups 1, 2a, 2b, and 2b'. Antimicrob Agents Chemother 1989; 33:264-70. [PMID: 2658780 PMCID: PMC171477 DOI: 10.1128/aac.33.3.264] [Citation(s) in RCA: 164] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Affiliation(s)
- K Bush
- Squibb Institute for Medical Research, Princeton, New Jersey 08540
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17
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Arakawa Y, Ohta M, Kido N, Mori M, Ito H, Komatsu T, Fujii Y, Kato N. Chromosomal beta-lactamase of Klebsiella oxytoca, a new class A enzyme that hydrolyzes broad-spectrum beta-lactam antibiotics. Antimicrob Agents Chemother 1989; 33:63-70. [PMID: 2653216 PMCID: PMC171422 DOI: 10.1128/aac.33.1.63] [Citation(s) in RCA: 95] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The chromosomally encoded beta-lactamase gene of Klebsiella oxytoca E23004, a strain resistant to cefoperazone and aztreonam, was cloned and expressed in Escherichia coli HB101. The molecular mass and pI of this enzyme were 28 kilodaltons and 7.4, respectively. Although the beta-lactamase of K. oxytoca hydrolyzed many cephalosporins, including broad-spectrum drugs, the nucleotide sequence and deduced amino acid sequence lacked homology with chromosomal class C beta-lactamase genes (ampC) of E. coli or Citrobacter freundii. Rather, about 45% nucleotide sequence homology and 40% deduced amino acid sequence homology were observed between the K. oxytoca beta-lactamase and TEM-1, a class A beta-lactamase which does not efficiently hydrolyze cephalosporins. Values of Km, relative Vmax, and relative Vmax/Km for the K. oxytoca beta-lactamase indicated that the enzyme is a penicillinase but that it can hydrolyze cefoperazone effectively and other broad-spectrum cephems weakly. Hence, the chromosomal beta-lactamase of K. oxytoca E23004 belongs to class A but differences in its amino acid sequence provide a broader spectrum of activity.
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Affiliation(s)
- Y Arakawa
- Department of Bacteriology, Nagoya University School of Medicine, Japan
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18
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Baumann M, Simon H, Schneider KH, Danneel HJ, Küster U, Giffhorn F. Susceptibility of Rhodobacter sphaeroides to beta-lactam antibiotics: isolation and characterization of a periplasmic beta-lactamase (cephalosporinase). J Bacteriol 1989; 171:308-13. [PMID: 2783689 PMCID: PMC209588 DOI: 10.1128/jb.171.1.308-313.1989] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Thirteen strains of the gram-negative, facultative phototrophic bacterium Rhodobacter sphaeroides were examined fro susceptibility to beta-lactam antibiotics. All strains were sensitive to the semisynthetic penicillins ampicillin, carbenicillin, oxacillin, cloxacillin, and methicillin, but 10 of the 13 strains were resistant to penicillin G, as well as a number of cephalosporins, such as cephalothin, cephapirin, and cephalosporin C. A beta-lactamase (EC 3.5.2.6) with strong cephalosporinase activity was detected in all of the resistant strains of R. sphaeroides. With strain Y-1 as a model, it was shown that the beta-lactamase was inducible by penicillin G, cephalosporin C, cephalothin, and to some minor extent, cephapirin. The beta-lactamase was located in the periplasmic space, from which it could be extracted by osmotic shock disruption. By using this fraction, the beta-lactamase was purified 34-fold to homogeneity by steps involving batch adsorption to and elution from DEAE-Sephadex A50, chromatography on Q-Sepharose, and preparative polyacrylamide gel electrophoresis. The molecular masses of the native and denatured enzymes were determined to be 38.5 kilodaltons by gel filtration and 40.5 kilodaltons by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, respectively, indicating a monomeric structure. The isoelectric point was estimated to be at pH 4.3. In Tris hydrochloride buffer, optimum enzyme activity was measured at pH 8.5. The beta-lactamase showed high activity in the presence of the substrates cephalothin, cephapirin, cephalosporin C, and penicillin G, for which the apparent Km values were 144, 100, 65, and 110 microM, respectively. Cephalexin, cepharidine, and cephaloridine were poor substrates. The beta-lactamase was strongly inhibited by cloxacillin and oxacillin but only slightly inhibited by phenylmethylsulfonyl fluoride or thiol reagents such as iodoacetate and p-chloromercuribenzoate.
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Affiliation(s)
- M Baumann
- Institut für Mikrobiologie der Universität Göttingen, Federal Republic of Germany
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19
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Galleni M, Frère JM. A survey of the kinetic parameters of class C beta-lactamases. Penicillins. Biochem J 1988; 255:119-22. [PMID: 3264154 PMCID: PMC1135198 DOI: 10.1042/bj2550119] [Citation(s) in RCA: 83] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The interaction between six class C beta-lactamases and various penicillins has been studied. All the enzymes behaved in a very uniform manner. Benzylpenicillin exhibited relatively low kcat. values (14-75 s-1) but low values of Km resulted in high catalytic efficiencies [kcat./Km = 10 X 10(6)-75 X 10(6) M-1.s-1]. The kcat. values for ampicillin were 10-100-fold lower. Carbenicillin, oxacillin cloxacillin and methicillin were very poor substrates, exhibiting kcat. values between 1 x 10(-3) and 0.1 s-1. The Km values were correspondingly small. It could safely be hypothesized that, with all the tested substrates, deacylation was rate-limiting, resulting in acyl-enzyme accumulation.
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Affiliation(s)
- M Galleni
- Laboratoire d'Enzymologie, Université de Liège, Sart Tilman, Belgium
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20
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21
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Abstract
The interaction between imipenem, a carbapenem antibiotic, and two representative beta-lactamases has been studied. The first enzyme was beta-lactamase I, a class-A beta-lactamase from Bacillus cereus; imipenem behaved as a slow substrate (kcat. 6.7 min-1, Km 0.4 mM at 30 degrees C and at pH 7) that reacted by a branched pathway. There was transient formation of an altered species formed in a reversible reaction; this species was probably an acyl-enzyme in a slightly altered, but considerably more labile, conformation. The kinetics of the reaction were investigated by measuring both the concentration of the substrate and the activity of the enzyme, which fell and then rose again more slowly. The second enzyme was the chromosomal class-C beta-lactamase from Pseudomonas aeruginosa; imipenem was a substrate with a low kcat. (0.8 min-1) and a low Km (0.7 microM). Possible implications for the clinical use of imipenem are considered.
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Affiliation(s)
- J Monks
- Sir William Dunn School of Pathology, University of Oxford, U.K
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22
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Jaurin B, Forsman M, Häggström B. Beta-lactamase genes of Streptomyces badius, Streptomyces cacaoi and Streptomyces fradiae: cloning and expression in Streptomyces lividans. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 949:288-96. [PMID: 2831988 DOI: 10.1016/0167-4781(88)90154-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Genes encoding extracellular beta-lactamases (EC 3.5.2.6) of Gram-positive Streptomyces badius, Streptomyces cacaoi and Streptomyces fradiae have been cloned into Streptomyces lividans. The beta-lactamase gene of S. badius was initially isolated on a 7 kb BamHI fragment and further located on a 1300 bp DNA segment. An 11 kb BamHI fragment was isolated encompassing the S. cacaoi beta-lactamase gene, which was subcloned to a 1250 bp DNA fragment. The beta-lactamase gene of S. fradiae was cloned on an 8 kb BamHI fragment and mapped to a 4 kb DNA segment. Each of the three BamHI fragments encompassing the beta-lactamase genes hybridized to a BamHI fragment of the corresponding size in chromosomal DNA from the respective strain used for cloning. The activities of the three beta-lactamases were predominantly found to be extracellular in the S. lividans recombinants. The S. badius and S. cacaoi beta-lactamases exhibited a 10-100-times lower activity in S. lividans, whereas the S. fradiae beta-lactamase showed an approximately 10-fold higher activity in the cloned state, compared with the activities found in the original strains.
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Affiliation(s)
- B Jaurin
- Department of Cell and Microbiology, National Defence Research Institute, Umeå, Sweden
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23
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Galleni M, Lindberg F, Normark S, Cole S, Honore N, Joris B, Frere JM. Sequence and comparative analysis of three Enterobacter cloacae ampC beta-lactamase genes and their products. Biochem J 1988; 250:753-60. [PMID: 3260487 PMCID: PMC1148921 DOI: 10.1042/bj2500753] [Citation(s) in RCA: 112] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The sequences of three Enterobacter cloacae ampC beta-lactamase genes have been determined. The deduced amino acid sequences are very similar: out of a total of 361 residues, only eight positions were found to be variable, and several mutations yielded residues with very similar properties. The kinetic properties of two of the enzymes were not significantly different. The three enzymes also exhibited a high degree of homology (greater than 70%) with the ampC beta-lactamases of Escherichia coli K12 and Citrobacter freundii, confirming the homogeneity of class-C beta-lactamases.
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Affiliation(s)
- M Galleni
- Université de Liège, Institut de Chimie, Belgium
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24
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Madgwick PJ, Waley SG. beta-lactamase I from Bacillus cereus. Structure and site-directed mutagenesis. Biochem J 1987; 248:657-62. [PMID: 3124817 PMCID: PMC1148599 DOI: 10.1042/bj2480657] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The sequence of the gene for beta-lactamase I from Bacillus cereus 569/H has been redetermined. Oligonucleotide-directed mutagenesis has been carried out, and the effects of the changes on the ampicillin-resistance of Escherichia coli TG1 expressing the mutant genes have been studied. Lysine-73, close to the active-site serine-70 and a highly-conserved residue, has been converted into arginine. This change had a large effect on activity, but did not abolish it. An even larger effect was found in the mutant in which glutamate-166 had been converted into glutamine; this had little or no activity. On the other hand, the conversion of glutamate-168 into aspartate gave fully active enzyme. Glutamate-166 is an invariant residue, but glutamate-168 is not. Alanine-123 has been replaced by cysteine, to give active enzyme; this change forms part of the plan to introduce a disulphide bond into the enzyme.
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Affiliation(s)
- P J Madgwick
- Sir William Dunn School of Pathology, University of Oxford, U.K
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25
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Yamaguchi A, Adachi H, Sawai T. Identification of the active site of Citrobacter freundii beta-lactamase using dansyl-penicillin. FEBS Lett 1987; 218:126-30. [PMID: 3496243 DOI: 10.1016/0014-5793(87)81031-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The active site sequence of a beta-lactamase encoded by chromosomal gene(s) in Citrobacter freundii GN346 was determined using dansyl-penicillin as a fluorescent probe. The tryptic digest of the labelled enzyme gave a fluorescent peptide containing 22 amino acids. The sequence of this peptide was identical to the consensus sequence of class C beta-lactamases, Gly-Ser-X-Ser-Lys. The residue labelled was the serine adjacent to the glycine. The active site sequence corresponded to positions 46-67 of the entire sequence of the Citrobacter freundii beta-lactamase determined on the basis of the DNA sequence of the structural gene [(1986) Eur. J. Biochem. 156, 441-445]. The labelled serine corresponded to Ser-64.
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26
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Duez C, Piron-Fraipont C, Joris B, Dusart J, Urdea MS, Martial JA, Frère JM, Ghuysen JM. Primary structure of the Streptomyces R61 extracellular DD-peptidase. 1. Cloning into Streptomyces lividans and nucleotide sequence of the gene. EUROPEAN JOURNAL OF BIOCHEMISTRY 1987; 162:509-18. [PMID: 3830154 DOI: 10.1111/j.1432-1033.1987.tb10669.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
An 11,450-base DNA fragment containing the gene for the extracellular active-site serine DD-peptidase of Streptomyces R61 was cloned in Streptomyces lividans using the high-copy-number plasmid pIJ702 as vector. Amplified expression of the excreted enzyme was observed. Producing clones were identified with the help of a specific antiserum directed against the pure DD-peptidase. The coding sequence of the gene was then located by hybridization with a specific nucleotide probe and sub-fragments were obtained from which the nucleotide sequence of the structural gene and the putative promoter and terminator regions were determined. The sequence suggests that the gene codes for a 406-amino-acid protein precursor. When compared with the excreted, mature DD-peptidase, this precursor possesses a cleavable 31-amino-acid N-terminal extension which has the characteristics of a signal peptide, and a cleavable 26-amino-acid C-terminal extension. On the basis of the data of Joris et al. (following paper in this journal), the open reading frame coding for the synthesis of the DD-peptidase was established. Comparison of the primary structure of the Streptomyces R61 DD-peptidase with those of several active-site serine beta-lactamases and penicillin-binding proteins of Escherichia coli shows homology in those sequences that comprise the active-site serine residue. When the comparison is broadened to the complete amino acid sequences, significant homology is observed only for the pair Streptomyces R61 DD-peptidase/Escherichia coli ampC beta-lactamase (class C). Since the Streptomyces R61 DD-peptidase and beta-lactamases of class A have very similar three-dimensional structures [Kelly et al. (1986) Science (Wash. DC) 231, 1429-1431; Samraoui et al. (1986) Nature (Lond.) 320, 378-380], it is concluded that these tertiary features are probably also shared by the beta-lactamases of class C, i.e. that the Streptomyces R61 DD-peptidase and the beta-lactamases of classes A and C are related in an evolutionary sense.
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27
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Abstract
Cephalosporins, like other beta-lactams, bind to the bacterial penicillin-binding proteins (PBPs). These correspond to the D-ala-D-ala trans-, carboxy- and endo-peptidases responsible for catalysing the cross-linking of newly formed peptidoglycan. Resistance arises when the PBPs-and particularly the transpeptidases-are modified, or when they are protected by beta-lactamases or 'permeability barriers'. Target-mediated cephalosporin resistance can involve either reduced affinity of an existing PBP component, or the acquisition of a supplementary beta-lactam-insensitive PBP. beta-lactamases are produced widely by bacteria and may be determined by chromosomal or plasmid DNA. The chromosomal beta-lactamases are species-specific, but can be classified into a few broad groups. The plasmid-mediated enzymes cross interspecific and intergeneric boundaries. The level of beta-lactamase-mediated resistance relates to the amount of enzyme produced with or without induction; to the location of the enzyme (extracellular for Gram-positive organisms and periplasmic in Gram-negative ones); and to the kinetics of the enzyme's activity. In Gram-positive organisms the PBPs are located on the outer aspect of the cytoplasmic membrane and so shielding by permeability barriers is minimal. In Gram-negative cells, however, the PBPs are protected by the outer membrane, which most beta-lactams cross by diffusion through aqueous pores composed of 'porin' proteins. In enterobacteria, a clear correlation exists between porin quantity and cephalosporin resistance, suggesting that the outer membrane is the sole barrier to drug entry. Such relationships are less clear for Pseudomonas aeruginosa, where the cell may contain additional barriers between the outer membrane and the PBPs. Although elevated cephalosporin resistance often is attributed to a single factor (PBP-modification, beta-lactamase action or impermeability) an organism's response to a drug often reflects the interplay of several factors. Mathematical models can be proposed to describe this interplay.
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Affiliation(s)
- D M Livermore
- Department of Medical Microbiology, London Hospital Medical College
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28
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Joris B, De Meester F, Galleni M, Masson S, Dusart J, Frère JM, Van Beeumen J, Bush K, Sykes R. Properties of a class C beta-lactamase from Serratia marcescens. Biochem J 1986; 239:581-6. [PMID: 3548700 PMCID: PMC1147326 DOI: 10.1042/bj2390581] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
A beta-lactamase produced by a penicillin-resistant strain of Serratia marcescens was isolated and purified. The kcat. value for benzylpenicillin was about 5% of that observed for the best cephalosporin substrates. However, the low Km of the penam resulted in a high catalytic efficiency (kcat./Km) and the classification of the enzyme as a cephalosporinase might not be completely justified. It also exhibited a low but measurable activity against cefotaxime, cefuroxime, cefoxitin and moxalactam. Substrate-induced inactivation was observed both with a very good (cephalothin) or a very bad (moxalactam) substrate. The active site was labelled by beta-iodopenicillanate. Trypsin digestion produced a 19-residue active-site peptide whose sequence clearly allowed the classification of the enzyme as a class C beta-lactamase.
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29
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Hakenbeck R, Briese T, Ellerbrok H. Antibodies against the benzylpenicilloyl moiety as a probe for penicillin-binding proteins. EUROPEAN JOURNAL OF BIOCHEMISTRY 1986; 157:101-6. [PMID: 3011428 DOI: 10.1111/j.1432-1033.1986.tb09644.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Antibodies against the benzylpenicilloyl determinant were used to identify complexes of benzylpenicilloyl and penicillin binding protein (PBP) of several bacterial species on immunoblots. Since radioactive penicillin was not needed, this technique readily allowed in vivo labeling studies even in Escherichia coli, where the saturating concentration was around 0.6 mg/ml. The antibodies showed no substantial cross-reactivity to other beta-lactam-PBP complexes with the exception of 6-aminopenicillanic acid. Surprisingly, some penicilloyl-PBP were hardly recognized by the antiserum, whereas the others could be stained according to the amount of penicillin bound.
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30
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Lindberg F, Normark S. Sequence of the Citrobacter freundii OS60 chromosomal ampC beta-lactamase gene. EUROPEAN JOURNAL OF BIOCHEMISTRY 1986; 156:441-5. [PMID: 3486121 DOI: 10.1111/j.1432-1033.1986.tb09601.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The Citrobacter freundii OS60 ampC beta-lactamase gene was sequenced and found to encode a 380-amino-acid-long precursor with a 19-residue signal peptide. The mature protein has a predicted molecular mass of 39781 Da. The first 60 residues of the purified enzyme, as determined by sequential Edman degradation, are identical to the amino acid sequence inferred from the gene sequence. Also, the amino acid composition determined for the purified beta-lactamase and that given by the gene sequence are in good agreement. 77% of the amino acid positions hold identical residues in the C. freundii and Escherichia coli K12 chromosomal AmpC beta-lactamases. This clearly puts the C. freundii enzyme into the class C of beta-lactamases. Of the 68 amino-terminal residues determined for the Enterobacter cloacae P99 beta-lactamase, 44 are identical to the corresponding residues of the C. freundii enzyme. All three enzymes, as well as that of Pseudomonas aeruginosa 18S/H are highly similar around the active-site serine at position 64 of the mature protein.
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31
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Boyd DB, Ott JL. Lack of relevance of kinetic parameters for exocellular DD-peptidases to cephalosporin MICs. Antimicrob Agents Chemother 1986; 29:774-80. [PMID: 3729340 PMCID: PMC284153 DOI: 10.1128/aac.29.5.774] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
MICs of a set of cephalosporins against a variety of gram-positive and gram-negative pathogens showed no strong correlations with the rate at which these inhibitors acylate or are deacylated by beta-lactam-sensitive DD-peptidases excreted by Streptomyces sp. strain R61 and Actinomadura sp. strain R39.
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32
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Houba-Hérin N, Hara H, Inouye M, Hirota Y. Binding of penicillin to thiol-penicillin-binding protein 3 of Escherichia coli: identification of its active site. MOLECULAR & GENERAL GENETICS : MGG 1985; 201:499-504. [PMID: 3911028 DOI: 10.1007/bf00331346] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
In order to determine the active site of penicillin-binding protein 3 of Escherichia coli (PBP3), the serine residue at position 307 was replaced with alanine, threonine or cysteine by oligonucleotide-directed site-specific mutagenesis. Since a unique BanII site exists at the position corresponding to serine-307, BanII digestion of the plasmid DNA after mutagenesis resulted in significant enrichment of the mutant plasmids. For mutagenesis, the gene coding for PBP3 (ftsI) was inserted into the expression cloning vector pIN-IIB. The hybrid protein produced was able to bind penicillin while mutant PBP3 in which serine-307 was replaced with either alanine or threonine did not lead to any detectable binding. However, contrary to the report of Broome-Smith et al. (1985) thiol-penicillin-binding protein 3, in which serine-307 was replaced with cysteine, was still able to bind penicillin. Replacement of serine-445 with an alanine residue had no effect on penicillin binding to PBP3.
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33
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Nicholas RA, Strominger JL, Suzuki H, Hirota Y. Identification of the active site in penicillin-binding protein 3 of Escherichia coli. J Bacteriol 1985; 164:456-60. [PMID: 3900044 PMCID: PMC214265 DOI: 10.1128/jb.164.1.456-460.1985] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
We report the sequence of the active site tryptic peptide of penicillin-binding protein 3 from Escherichia coli. Purified penicillin-binding protein 3 was labeled with [14C]penicillin G and digested with trypsin, and the resulting radioactive peptides were isolated by a combination of gel filtration and high-pressure liquid chromatography. The major radioactive peak from high-pressure liquid chromatography was sequenced, and the peptide Thr-Ile-Thr-Asp-Val-Phe-Glu-Pro-Gly-Ser-Thr-Val-Lys, which comprises residues 298 to 310 in the amino acid sequence, was identified. This sequence is compared with the active site sequences from other penicillin-binding proteins and beta-lactamases.
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34
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35
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Bicknell R, Emanuel EL, Gagnon J, Waley SG. The production and molecular properties of the zinc beta-lactamase of Pseudomonas maltophilia IID 1275. Biochem J 1985; 229:791-7. [PMID: 3931629 PMCID: PMC1145126 DOI: 10.1042/bj2290791] [Citation(s) in RCA: 73] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The production and purification of a tetrameric zinc beta-lactamase from Pseudomonas maltophilia IID 1275 were greatly improved. Three charge variants were isolated by chromatofocusing. The subunits each contain two atomic proportions of zinc and (in two of the variants) one residue of cysteine. The thiol group is not required for activity, nor does it appear to bind to the metal. Replacement of zinc by cobalt, cadmium or nickel takes place at a measurable rate, and gives enzymes that are less active than the zinc enzyme. The properties of this enzyme differ from those of the other known zinc beta-lactamase, beta-lactamase II from Bacillus cereus. The amino acid sequence of the N-terminal 32 residues was determined; there is no similarity to the N-terminal sequences of other beta-lactamases.
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36
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The beta-lactamase of Enterobacter cloacae P99. Chemical properties, N-terminal sequence and interaction with 6 beta-halogenopenicillanates. Biochem J 1985; 228:241-8. [PMID: 2988516 PMCID: PMC1144975 DOI: 10.1042/bj2280241] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The beta-lactamase of Enterobacter cloacae P99 consists of one polypeptide chain of Mr 39000 devoid of disulphide bridges and free thiol groups. It contains an unusually high proportion of tyrosine and tryptophan. The N-terminal sequence exhibits overlaps with the tryptic peptide obtained after labelling the active site with 6 beta-iodopenicillanate. The active-site serine residue is at position 64. The homology with the chromosomal beta-lactamase of Escherichia coli K 12 (ampC gene) is lower within the 25 residues of the N-terminal portion than around the active-site serine residue. The P99 beta-lactamase is inactivated by 6 beta-bromo- and 6 beta-iodo-penicillanate, with a second-order rate constant of 110-140M-1 X s-1 at 30 degrees C and pH 7.0, a value that is much lower than that observed with class-A beta-lactamases.
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2.8-A Structure of penicillin-sensitive D-alanyl carboxypeptidase-transpeptidase from Streptomyces R61 and complexes with beta-lactams. J Biol Chem 1985. [DOI: 10.1016/s0021-9258(18)88993-1] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Keck W, Glauner B, Schwarz U, Broome-Smith JK, Spratt BG. Sequences of the active-site peptides of three of the high-Mr penicillin-binding proteins of Escherichia coli K-12. Proc Natl Acad Sci U S A 1985; 82:1999-2003. [PMID: 3920658 PMCID: PMC397473 DOI: 10.1073/pnas.82.7.1999] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The amino acid compositions of the radioactive peptides obtained from trypsin digestion of [14C]benzylpenicillin-labeled penicillin-binding proteins (PBPs) 1A, 1B, and 3 of Escherichia coli have been obtained. Complete digestion of these peptides with a combination of aminopeptidase M and carboxypeptidase Y showed that benzylpenicillin was bound to a serine residue in each of these proteins. Comparison of the compositions of the penicillin-labeled peptides with the complete amino acid sequences of PBPs 1A, 1B, and 3 showed that the acylated serine occurs near the middle of each of the proteins, within the conserved sequence Gly-Ser-Xaa-Xaa-Lys-Pro. The sequence around the acylated serine of these high Mr PBPs shows little similarity to that around the acylated serine of the low-Mr PBPs (D-alanine carboxypeptidases) or of the class A or class C beta-lactamases, except that in all of these enzymes which interact with penicillin the acylated serine residue occurs within the sequence Ser-Xaa-Xaa-Lys.
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Broome-Smith JK, Edelman A, Yousif S, Spratt BG. The nucleotide sequences of the ponA and ponB genes encoding penicillin-binding protein 1A and 1B of Escherichia coli K12. EUROPEAN JOURNAL OF BIOCHEMISTRY 1985; 147:437-46. [PMID: 3882429 DOI: 10.1111/j.1432-1033.1985.tb08768.x] [Citation(s) in RCA: 97] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Penicillin-binding proteins 1A and 1B of Escherichia coli are the major peptidoglycan transglycosylase-transpeptidases that catalyse the polymerisation and insertion of peptidoglycan precursors into the bacterial cell wall during cell elongation. The nucleotide sequence of a 2764-base-pair fragment of DNA that contained the ponA gene, encoding penicillin-binding protein 1A, was determined. The sequence predicted that penicillin-binding protein 1A had a relative molecular mass of 93 500 (850 amino acids). The amino-terminus of the protein had the features of a signal peptide but it is not known if this peptide is removed during insertion of the protein into the cytoplasmic membrane. The nucleotide sequence of a 2758-base-pair fragment of DNA that contained the ponB gene, encoding penicillin-binding protein 1B, was also determined. Penicillin-binding protein 1B consists of two major components which were shown to result from the use of alternative sites for the initiation of translation. The large and small forms of penicillin-binding protein 1B were predicted to have relative molecular masses of 94 100 and 88 800 (844 and 799 amino acids). The amino acid sequences of penicillin-binding proteins 1A and 1B could be aligned if two large gaps were introduced into the latter sequence and the two proteins then showed about 30% identity. The amino acid sequences of the proteins showed no extensive similarity to the sequences of penicillin-binding proteins 3 or 5, or to the class A or class C beta-lactamases. Two short regions of amino acid similarity were, however, found between penicillin-binding proteins 1A and 1B and the other penicillin-binding proteins and beta-lactamases. One of these included the predicted active-site serine residue which was located towards the middle of the sequences of penicillin-binding proteins 1A, 1B and 3, within the conserved sequence Gly-Ser-Xaa-Xaa-Lys-Pro. The other region was 19-40 residues to the amino-terminal side of the active-site serine and may be part of a conserved penicillin-binding site in these proteins.
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Inhibition of class C beta-lactamases by (1'R,6R)-6-(1'-hydroxy)benzylpenicillanic acid SS-dioxide. Biochem J 1985; 225:435-9. [PMID: 2983675 PMCID: PMC1144608 DOI: 10.1042/bj2250435] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
beta-Lactamases, enzymes that catalyse the hydrolysis of the beta-lactam ring in beta-lactam antibiotics, are divided into three classes, A, B and C, on the basis of the structures so far determined. There are relatively few effective inhibitors of class C beta-lactamases. A beta-lactam sulphone with a hydroxybenzyl side chain, namely (1'R,6R)-6-(1'-hydroxy)benzylpenicillanic acid SS-dioxide (I), has now been studied. The sulphone is a good mechanism-based inhibitor of class C beta-lactamases. At pH8, the inhibition of a Pseudomonas beta-lactamase is irreversible, and proceeds at a rate that is about one-tenth the rate of concurrent hydrolysis. The labelled enzyme has enhanced u.v. absorption and is probably an enamine. At a lower pH, however, inhibition is transitory.
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Hedge PJ, Spratt BG. A gene fusion that localises the penicillin-binding domain of penicillin-binding protein 3 of Escherichia coli. FEBS Lett 1984; 176:179-84. [PMID: 6092133 DOI: 10.1016/0014-5793(84)80936-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
A gene fusion that links the COOH-terminal 349 amino acids of penicillin-binding protein 3 (60 kDa) of E. coli to the NH2-terminus of beta-galactosidase has been constructed. The fusion protein (38.5 kDa) retains the ability to bind benzylpenicillin with high affinity, establishing that the penicillin-binding domain (and presumably the penicillin-sensitive transpeptidase activity) of this high molecular mass penicillin-binding protein is located on a COOH-terminal functional domain.
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Joris B, Dusart J, Frere JM, van Beeumen J, Emanuel EL, Petursson S, Gagnon J, Waley SG. The active site of the P99 beta-lactamase from Enterobacter cloacae. Biochem J 1984; 223:271-4. [PMID: 6333871 PMCID: PMC1144291 DOI: 10.1042/bj2230271] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Labelling the beta-lactamase of Enterobacter cloacae P99 with a poor substrate or a mechanism-based inactivator points to an active-site serine residue in a sequence closely resembling that of the ampC beta-lactamase. These results establish the P99 enzyme as a class-C beta-lactamase, and the concurrence of the two approaches helps to confirm the reliability of determining active-site sequences with the aid of mechanism-based inactivators.
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Cartwright SJ, Waley SG. Purification of beta-lactamases by affinity chromatography on phenylboronic acid-agarose. Biochem J 1984; 221:505-12. [PMID: 6332621 PMCID: PMC1144066 DOI: 10.1042/bj2210505] [Citation(s) in RCA: 126] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Several beta-lactamases, enzymes that play an important part in antibiotic resistance, have been purified by affinity chromatography on boronic acid gels. The procedure is rapid, appears to be selective for beta-lactamases, and allows a one-step purification of large amounts of enzyme from crude cell extracts. We have found the method useful for any beta-lactamase that is inhibited by boronic acids. Two kinds of boronic acid column have been prepared, the more hydrophobic one being reserved for those beta-lactamases that bind boronic acids relatively weakly. beta-Lactamase I from Bacillus cereus, P99 beta-lactamase and K 1 beta-lactamase from Gram-negative bacteria are among the better-known beta-lactamases that have been purified by this method. The procedure has also been used to purify a novel beta-lactamase from Pseudomonas maltophilia in high yield; the enzyme has an exceptionally broad substrate profile and hydrolyses monocyclic beta-lactams such as azthreonam and desthiobenzylpenicillin.
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Abstract
In summary, Table XVI shows the inhibition profiles of representative beta-lactamases from each major class of Richmond and Sykes. Either resistance (R) or sensitivity (S) is given as a general guide to the type of compounds likely to inhibit each class. Thus the (qualitative) statements regarding the effectiveness of clavulanic acid can be taken to represent those for the penam sulfones and similarly for MM4550 and the other olivanic acids, carpetimycins, PS series, and asparenomycins. This can also be said of cloxacillin and the other aromatic carboxamido penicillins. Compounds are also included which are specifically or particularly inhibitory to certain beta-lactamases.
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Bergström S, Lindberg FP, Olsson O, Normark S. Comparison of the overlapping frd and ampC operons of Escherichia coli with the corresponding DNA sequences in other gram-negative bacteria. J Bacteriol 1983; 155:1297-305. [PMID: 6350266 PMCID: PMC217828 DOI: 10.1128/jb.155.3.1297-1305.1983] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Specific DNA probes from Escherichia coli K-12 were used to analyze the sequence divergence of the frd and ampC operons in various species of gram-negative bacteria. These operons code for the fumarate reductase complex and the chromosomal beta-lactamase, respectively. We demonstrate that the two operons show the same general pattern of divergence, although the frd operon is considerably more conserved than is the ampC operon. The major exception is Salmonella typhimurium LT2, which shows a strong homology to the E. coli frd probe but none to the E. coli ampC probe. The operons from Citrobacter freundii and Shigella sonnei were cloned and characterized by physical mapping, Southern hybridization, and protein synthesis in minicells. In S. sonnei, as in E. coli K-12, the frd and ampC operons overlap (T. Grundström and B. Jaurin, Proc. Natl. Acad. Sci. U.S.A. 79:1111-1115, 1982). Only minor discrepancies between the two operons were found over the entire frd-ampC region. In C. freundii, the ampC and frd operons do not overlap, being separated by about 1,100 base pairs. Presumably the inducible property of the C. freundii chromosomal beta-lactamase is encoded by this 1,100-base-pair DNA segment.
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Bicknell R, Knott-Hunziker V, Waley SG. The pH-dependence of class B and class C beta-lactamases. Biochem J 1983; 213:61-6. [PMID: 6604522 PMCID: PMC1152090 DOI: 10.1042/bj2130061] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The classification by structure allots beta-lactamases to (at present) three classes, A, B and C. The pH-dependence of the kinetic parameters for class B and class C have been determined. They differ from each other and from class A beta-lactamases. The class B enzyme was beta-lactamase II from Bacillus cereus 569/H/9. The plots of kcat against pH for the hydrolysis of benzylpenicillin by Zn(II)-requiring beta-lactamase II and Co(II)-requiring beta-lactamase II were not symmetrical, but those of kcat/Km were. A similar feature was observed for the hydrolysis of both benzylpenicillin and cephalosporin C by a class C beta-lactamase from Pseudomonas aeruginosa. The results have been interpreted by a scheme in which two ionic forms of an intermediate can give product, but do so at differing rates.
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Arisawa M, Adam S. Mechanism of inactivation of TEM-1 beta-lactamase by 6-acetylmethylenepenicillanic acid. Biochem J 1983; 211:447-54. [PMID: 6307281 PMCID: PMC1154378 DOI: 10.1042/bj2110447] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The interaction between 6-acetylmethylenepenicillanic acid (compound Ro 15-1903; AMPA) and TEM-1 beta-lactamase was investigated in order to elucidate the mechanism of action of AMPA. Formation of the enzyme-inhibitor complex (EA) was accompanied by a shift of the absorbance maximum from 292 nm to 303 nm and an increase in the absorption. Regeneration of activity was very slow and incomplete, reaching about one-third of the initial activity after 48 h at 37 degrees C. This behaviour indicated a branched pathway of the decay of the inactivated enzyme. Kinetic and isoelectric-focusing experiments proved this assumption. The first-order constant of regeneration of active enzyme was 6 X 10(-6)-10 X 10(-6) s-1, whereas the rate constant leading to inactive enzyme (EA') was 10 X 10(-6)-15 X 10(-6) s-1 at pH 7.0. Both constants became larger at higher pH. Inactive enzyme (EA') consisted of two major species, with pI 5.36 (EA'1) and 5.30 (EA'2). The former increased at the beginning of incubation but decreased after prolonged incubation. From consideration of these results and previous data [Arisawa & Then (1983) Biochem. J. 209, 609-615], a likely mechanism of inactivation of TEM-1 beta-lactamase by AMPA is discussed.
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Barthelemy M, Peduzzi J, Verchere-Beaur C, Brive-le Bouguenec C, Labia R. Single substitution in amino acid composition between TEM-2 β-lactamase and a variant with altered kinetic constants. FEMS Microbiol Lett 1983. [DOI: 10.1111/j.1574-6968.1983.tb00391.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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50
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Beesley T, Gascoyne N, Knott-Hunziker V, Petursson S, Waley SG, Jaurin B, Grundström T. The inhibition of class C beta-lactamases by boronic acids. Biochem J 1983; 209:229-33. [PMID: 6405733 PMCID: PMC1154076 DOI: 10.1042/bj2090229] [Citation(s) in RCA: 116] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Aromatic boronic acids are reversible inhibitors of the recently classified class C beta-lactamases. The boronic acids studied include ortho-, meta- and para-methyl-, -hydroxymethyl- and -formyl-phenylboronic acid. The beta-lactamases were chromosomally-encoded enzymes, one from Pseudomonas aeruginosa, and the other specified by the ampC gene of Escherichia coli. The inhibition may be correlated with our finding that these beta-lactamases are serine enzymes, i.e. their function entails the hydroxy group of a serine residue acting as a nucleophile.
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