Beta-lactamase is a key enzyme in antibiotic resistance, catalysing the cleavage of the essential beta-lactam ring structure in penicillin and cephalosporinase type antibiotics. Substrate specificity varies considerably within the beta-lactamases, with some enzymes preferring penicillins and some cephalosporins.
Defined by 5 residues: HIS:A-86HIS:A-88ASP:A-90HIS:A-149ASN:A-180