6-Aminopenicillanic acid V. 6-Aminopenicillanic acid as a substrate for penicillinase and an inducer of penicillinase formation

Abstract

The pH optimum for 6-aminopenicillanic acid hydrolysis by both staphylococcal and Bacillus cereus penicillinase is sharper and lower than for benzylpenicillin. With staphylococcal penicillinase the optimum is 5.6 compared with 6.5 to 7.0 for benzylpenicillin. Similarly, with B . cereus penicillinase the optimum is 5.5 compared with 7.0 for benzylpenicillin. The Michaelis constant for 6-aminopenicillanic acid with both types of penicillinase is relatively high compared with that for benzylpenicillin. With staphylococcal penicillinase the K m = 0.03 m compared with < 0.0003 for benzylpenicillin. With B . cereus penicillinase the K m = 0.003 m for 6-aminopenicillanic acid compared with 0.00006 m for benzylpenicillin. With staphylococcal penicillinase at the respective pH optima for 6-aminopenicillanic acid and benzylpenicillin the V max. for the two substrates is the same. With B . cereus penicillinase the V max. for 6-aminopenicillanic acid is slightly lower than the corresponding value for benzylpenicillin. 6-Aminopenicillanic acid induces the formation of staphylococcal penicillinase.