Protonation states and pKa values identified by the present work
1 and 5 represent irreversibly inactivated enzyme forms. Water/hydroxide ligation is presumed, and the protonation state of the proximal ligand is unknown. 2 is most active toward chlorite decomposition. According to the model presented in the text, 4 is moderately active while 3 may have little or no activity. Species 4, the alkaline form of the enzyme, has a mixture of HS and LS Fe.