<unk> s are enzymes (EC 3.5.2.6) produced by some bacteria and are responsible for their resistance to<unk> -lactam antibiotics like penicillins, cephalosporins, cephamycins and carbapenems. These antibiotics have a common element in their molecular structure: a four-atom ring known as a<unk> -lactam. The<unk>  enzyme breaks that ring open, deactivating the molecule's antibacterial properties.<unk> -lactame antibiotics are typically used to treat a broad spectrum of gram positive and gram-negative bacteria. <unk> s produced by gram-positive organisms are usually secreted.<unk>  may be clinically beneficial when orally administered to preserve the natural intestinal flora during the  parenteral administration of anti-biotics.  "This could provide protection against a broad range of nosocomial pathogens," per Dr. Usha Stiefel at the 47th annual Interscience Conference of Antimicrobial Agents and Chemotherapy.
The structure of a Streptomyces β<unk>  is given by PDB: 1BSG​.
Beta-lactamase
Pneumolysin
Clostridiopeptidase
Fibrinolysin
Proteogenix
Chlorotoxin
Brinase
Immunotoxin