ß-lactamase

ß-lactamase /ß-lac·ta·mase/ (lak´tah-mas) any of a group of enzymes, produced by almost all gram-negative bacteria, that hydrolyze the ß-lactam ring of penicillins and cephalosporins, destroying their antibiotic activity. Individual enzymes may be called penicillinases or cephalosporinases based on their specificities.

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ß-lactamase

either of two enzymes: ß-lactamase I is penicillinase; ß-lactamase II is cephalosporinase.