OXA-type beta-lactamases.
The OXA-type (oxacillin-hydrolysing) enzymes are widespread and have been mostly described in Enterobacteriaceae and in P. aeruginosa. They usually confer resistance to amino- and ureidopenicillin and possess high-level hydrolytic activity against cloxacillin, oxacillin, and methicillin. Their activities are weakly inhibited by clavulanic acid but sodium chloride (NaCl) possesses a strong inhibition activity. Oxacillin-hydrolysing b-lactamases belong to Ambler class D and thus possess an active serine site as classes A and C b-lactamases. Overall amino-acid identities between class D and class A or class C b-lactamases is about 16%. Until now, 24 Ambler class D enzymes, named OXA-1 to OXA-22, AmpS and LCR-1, have been characterised, either by sequence and/or by biochemical analyses, but for none of them a three dimensional structure is yet available. While some oxacillinases present a significant degree of amino-acid identity (for example, OXA-1 and OXA-4; OXA-10 (PSE-2) derivatives; OXA-2 and OXA-3), most of them are only weakly related (20% to 30% amino-acid identity). Oxacillinases usually display a restricted-spectrum phenotype. However extension of their spectrum towards oxyimino cephalosporins and/or imipenem has recently been observed mostly as a consequence of point mutations in OXA-2 or OXA-10 derivatives. Their frequent plasmid- and/or integron-location provide them a mean for a wide diffusion.
Naas
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Service de Bactériologie-Virologie, Hôpital de Bicêtre, 94274 Le Kremlin-Bicêtre, Assistance Publique-Hôpitaux de Paris, Faculté de Médecine Paris-Sud, Université Paris XI, Paris, France. thierry.naas@kb.u-psud.fr
Nordmann
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D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001483:Base Sequence; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D010068:Oxacillin / Q000494:pharmacology; D010406:Penicillins / Q000494:pharmacology; D010641:Phenotype; D018440:beta-Lactam Resistance / Q000502:physiology*; D001618:beta-Lactamases / Q000737:chemistry* / Q000145:classification / Q000235:genetics / Q000378:metabolism
D000900:Anti-Bacterial Agents; D010406:Penicillins; D001618:beta-Lactamases; D010068:Oxacillin