two types of substituents have been demonstrated to protect 1-oxacephem from enzymic hydrolysis and their protecting effects were specifically related to the types of beta-lactamases derived from gram-negative bacteria : the 7 beta-malonylamino function is specific to cephalosporinase and the 7 alpha-methoxy group to penicillinase .
C0597979
beta-lactamases
C0030841
penicillinase