While tazobactam is resistant to penicillinases, it does not have anti-bacterial activity. Elimination of thiotetrazole interferes with vitamin-K dependent clotting factors. B. C. Carbenecillin contains a net charge of -2 at physiological pH. Thus it is administered with two positively charged couterions. This will aggrivate the salt buildup. The electron withdrawling character of sidechain C contributes to acid stability of penams.
Penicillinases are newly evolved enzymes developed in response to our excess use of penicillin.
Penicillinases areevolutionarily related to the transpeptidases. Cycloserine is a structural analog of D-Alanine. A 6-methoxy group on penams generates effective compounds that are resistant to penicillinases. Alteration of the sugar moieties of the polysaccharide backbone of the peptidoglycan should be an effective way for the organism to become resistant to vancomycin. Acid proteases do not form acyl-enzyme intermediates like serine proteases.