Classification for beta-lactamases: historical perspectives

Introduction: beta-Lactamases are some of the most prevalent and well-studied families of enzymes, especially in the area of antibiotic resistance. Early attempts to categorize them used either functional names, such as penicillinase or cephalosporinase or structural designations into classes A and B. Increasing diversity of the properties of these enzymes has required a more expansive approach to nomenclature. Areas covered: Historical designations for early beta-lactamases relied heavily on functional names based on the biochemical properties of purified enzymes. As amino acid sequences began to be reported for a select group of these enzymes, classes of beta-lactamases were defined, with a major lumping of enzymes into those that had active site serine residues ( class A, C, and D) and those that were metallo-beta- lactamases ( MBLs or class B). More recent classification schemes, as determined through a Medline search, have attempted to incorporate both functional and structural features, using functional groups and subgroups to name beta-lactamases within the same structural class. Nomenclature of these enzymes is now under the purview of the NCBI (National Center for Biotechnology Information). Expert opinion: beta-Lactamase nomenclature will continue to evolve with the identification of new enzymes and new functionalities.