to all appearances , the beta-lactamase has no bivalent cation requirement whereas , as shown elsewhere [ dideberg , charlier , dupont , vermeire , frere & ghuysen ( 1980 ) febs lett . 117 , 212-214 , and dideberg , joris , frere , ghuysen , weber , robaye , delbrouck & roelands ( 1980 ) febs lett . 117 , 215-218 ] , the dd-carboxypeptidase possesses one essential zn2+ ion per molecule .
C0007447
cation
C0022023
ion