The ABCD's of β-lactamase nomenclature

J Infect Chemother. 2013 Aug;19(4):549-59. doi: 10.1007/s10156-013-0640-7. Epub 2013 Jul 5.


β-Lactamases can be named on the basis of molecular characteristics or functional properties. Molecular classes A, B, C, and D define an enzyme according to amino acid sequence and conserved motifs. Functional groups 1, 2, and 3 are used to assign a clinically useful description to a family of enzymes, with subgroups designated according to substrate and inhibitor profiles. In addition, other designations are used to define the functionality of specific subgroups, such as extended-spectrum β-lactamases, or ESBLs, and inhibitor-resistant TEM, or IRT, β-lactamases. None of these systems provides an unambiguous description of this versatile set of enzymes. A proposed classification system involving microbiological, molecular, and biochemical properties is described, based on the traditional classes A, B, C, and D and functional groups 1, 2, and 3 designations.

Publication types

  • Review

MeSH terms

  • Bacteria / drug effects
  • Bacteria / enzymology*
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / classification
  • Bacterial Proteins / metabolism
  • Terminology as Topic
  • beta-Lactamases / chemistry
  • beta-Lactamases / classification*
  • beta-Lactamases / metabolism


  • Bacterial Proteins
  • beta-Lactamases