o-Phenanthroline (anhydrous) is a heterocyclic organic compound, also named as 1,10-Phenanthroline, 1, ... of metallopeptidases, with one of the first observed instances reported in carboxypeptidase A. Inhibition of the enzyme occurs by removal and chelation ... inactive apoenzyme. 1,10-Phenanthroline targets mainly zinc metallopeptidases, with a much lower affinity for calcium.