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penicillinase pen·i·cil·li·nase (pěn'ĭ-sĭl'ĭ-nās')
Any of various enzymes, produced by certain bacteria, that hydrolyze and inactivate penicillin and are used in medicine to treat allergic reactions to penicillin. Also called beta-lactamase, cephalosporinase.
A purified enzyme preparation obtained from cultures of a strain of Bacillus cereus and formerly used to treat slowly developing or delayed penicillin reactions.