Beta-lactamase
Beta-lactamases are enzymes (EC 3.5.2.6) produced by some bacteria and are responsible for their resistance to beta-lactam antibiotics like penicillins, cephamycins, and carbapenems (ertapenem) (Carbapenems are relatively resistant to beta-lactamase). These antibiotics have a common element in their molecular structure: a four-atom ring known as a beta-lactam. The lactamase enzyme breaks the β-lactam ring open, deactivating the molecule's antibacterial properties.
Beta-lactam antibiotics are typically used to treat a broad spectrum of Gram-positive bacteria, as well as a few Gram-negative bacteria. Beta-lactamases produced by Gram-negative organisms are usually secreted.
The structure of a Streptomyces β lactamase is given by 1BSG.
Read more about Beta-lactamase: Penicillinase, Resistance in Gram-negative Bacteria