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$\cdot $6 compared with 6$\cdot $5 to 7$\cdot $0 for benzylpenicillin. Similarly, with B. cereus penicillinase the optimum is 5$\cdot $5 compared with 7$\cdot $0 for benzylpenicillin. The Michaelis constant for 6-aminopenicillanic acid with both types of penicillinase is relatively high compared with that for benzylpenicillin. With staphylococcal penicillinase the K$_{m}$ = 0$\cdot $03 M compared with < 0$\cdot $0003 for benzylpenicillin. With B. cereus penicillinase the K$_{m}$ = 0$\cdot $003 M for 6-aminopenicillanic acid compared with 0$\cdot $00006 M for benzylpenicillin. With staphylococcal penicillinase at the respective pH optima for 6-aminopenicillanic acid and benzylpenicillin the V$_{\text{max.}}$ for the two substrates is the same. With B. cereus penicillinase the V$_{\text{max.}}$ for 6-aminopenicillanic acid is slightly lower than the corresponding value for benzylpenicillin. 6-Aminopenicillanic acid induces the formation of staphylococcal penicillinase.