Plasmid-mediated penicillin beta-lactamases in Pseudomonas aeruginosa.

A penicillin beta-lactamase (PCase) was extracted from Pseudomonas aeruginosa Rms139(+) and purified by means of column chromatography. The isoelectric point of Rms139 PCase was 5.7 and its molecular weight was 22,500 +/- 1,000. The optimal pH for the hydrolysis of benzylpenicillin was 7.0 to 7.5 and the optimal temperature was 45 C, with the PCase also showing high activity against carbenicillin. It is concluded that this enzyme is a new type of penicillin beta-lactamase different from the type I, II, or III R plasmid-mediated PCases reported previously.