The interaction of penicillinase with penicillins III. Comparison of exopenicillinase preparations of various origins

• 1.

  1. The interaction of various penicillinases (penicillin amidohydrolase, EC 3.5.2.6) with methicillin and oxacillin has been studied.

• 2.

  2. The K_m values have been compared and found to reflect the phylogenetic and serological relationship of the penicillinases.

• 3.

  3. Methicillin and oxacillin accelerate the inactivation of penicillinases by heat and by urea, and expose groups sensitive to iodine and to p-chloromercuribenzoate (p-hydroxymercuribenzoate).

• 4.

  4. The response of penicillinases from different sources to various concentrations of these analogs has been compared.

• 5.

  5. The patterns of response are characteristic of the source of penicillinase, and essentially independent of the structure of the analog.

• 6.

  6. A comparison of these patterns brings out subtle differences in the tertiary structure of the active sites of closely related enzymes.

• 7.

  7. The sensitivity of such analysis is illustrated by the difference in reponse patterns of enzymically and serologically indistinguishable induced and constitutive enzyme preparations.