The metallo-β-lactamase produced by Chryseobacterium(formerly Flavobacterium) meningosepticum,which is the flavobacterial species of greatest clinical relevance, was purified and characterized. The enzyme, named BlaB, contains a polypeptide with an apparent Mr of 26000, and has a pI of 8.5. It hydrolyses penicillins, cephalosporins (including cefoxitin), carbapenems and 6-β-iodopenicillanate, a mechanism-based inactivator of active-site serine β-lactamases. The enzyme was inhibited by EDTA, 1-10 phenanthroline and pyridine-2,6-dicarboxylic acid, with different inactivation parameters for each chelating agent. The C. meningosepticum blaBgene was cloned and sequenced. According to the G+C content and codon usage, the blaBgene appeared to be endogenous to the species. The BlaB enzyme showed significant sequence similarity to other class B β-lactamases, being overall more similar to members of subclass B1, which includes the metallo-enzymes of Bacillus cereus(Bc-II) and Bacteroides fragilis(CcrA) and the IMP-1 enzyme found in various microbial species, and more distantly related to the metallo-β-lactamases of Aeromonasspp. (CphA, CphA2 and ImiS) and of Stenotrophomonas maltophilia(L1).

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