Exopenicillinase synthesis in Staphylococcus aureus.

In Staphylococcus aureus, penicillinase remaining cell-bound (60 to 75% of original total) after treatment with citrate does not become exopenicillinase. Exopenicillinase in these cells appears only under conditions permitting de novo penicillinase synthesis. By use of (14)C-labeled cells, it was shown that exopenicillinase consists of newly synthesized molecules which have not equilibrated with preformed membrane-bound enzyme.