class B (metallo-) beta-lactamase subclass B1 (metallo-) beta-lactamase antibiotic_resistance Subclass B1 possess a binuclear active site. Within this active site can be either one or two Zn(II) ions. This subclass is able to hydrolyze penicillins, cephalosporins and carbapenems. This is the most clinically relevant subclass of MBLs. ARO:3000568