Metallo-beta-lactamases: a class apart.
Metallo-beta-lactamases have recently become more prominent among the beta-lactam-hydrolyzing enzymes. Two major functional groups of enzymes have been identified, with little structural similarity among the groups. One group is a set of enzymes with broad substrate specificities capable of hydrolyzing most beta-lactams except monobactams. A second group is composed of the "true" carbapenemases, enzymes that exhibit poor hydrolysis of penicillins and cephalosporins. This latter group has been found primarily in Aeromonas species. To date, only a small number of carbapenem-resistant isolates have been reported to produce metallo-beta-lactamases, in part because of the ease with which this resistance can be acquired by other means: permeability changes and an increase in chromosomal cephalosporinase production. However, the appearance of these enzymes on plasmids in Japan poses a worrisome problem. It is anticipated that plasmid-mediated resistance to carbapenems will continue to increase, perhaps compromising the use of these agents.
Astra Research Center Boston, Cambridge, Massachusetts, USA.
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D006801:Humans; D008667:Metalloproteins / Q000096:biosynthesis / Q000737:chemistry / Q000145:classification; D011487:Protein Conformation; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000096:biosynthesis / Q000737:chemistry / Q000145:classification
D008667:Metalloproteins; D001618:beta-Lactamases