Beta-lactamase is a type of enzyme responsible for bacterial resistance to penicillin-type antibiotics. Penicillin and related antibiotics have a common element in their molecular structure, a four-atom ring known as a beta lactam (See ampicillin for an example of a penicillin structure). The lactamase enzyme breaks that ring down, rendering the molecule inactive as an antibiotic.

The structure of a Streptomyces β lactamase is given by PDB 1BSG EC

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