however , because the region around serine-80 of the ampc beta-lactamase has extensive homology with an active-site fragment of the pseudomonas aeruginosa cephalosporinase , we suggest that the ampc cephalosporinase as well as related cephalosporinases form a distinct group of serine beta-lactamases that have an evolutionary origin different from that of the serine penicillinases and thus constitute a new class of beta-lactamases .
C0597979
beta-lactamases
C0030841
penicillinases