Beta-lactamase - Penicillinase

Penicillinase

Penicillinase is a specific type of β-lactamase, showing specificity for penicillins, again by hydrolysing the beta-lactam ring. Molecular weights of the various penicillinases tend to cluster near 50 kiloDaltons.

Penicillinase was the first β-lactamase to be identified: It was first isolated by Abraham and Chain in 1940 from Gram-negative E. coli even before penicillin entered clinical use, but penicillinase production quickly spread to bacteria that previously did not produce it or produced it only rarely. Penicillinase-resistant beta-lactams such as methicillin were developed, but there is now widespread resistance to even these.