Calcium-related properties of horseradish peroxidase 

 -  BioChemical and Biophysical Research Communications, 80, p.1039-1042, 1978 .
<br/><br/> Horseradish peroxidase has been shown to be a metalloprotein in which calcium contributes to the structural stability of the protein. Isoenzyme C and A contain 2.0 and 1.4 moles calcium/mole enzyme, respectively, which can be removed by treatment with guanidine hydrochloride and EDTA. Calcium-free isoenzyme C, but not isoenzyme A, reconstitutes upon addition of calcium and regains enzymatic activity. Free calcium readily exchanges with isoenzyme C, but only to a small extent with isoenzyme A. In addition the role of calcium in maintaining molecular conformation is evidenced by the effects of calcium removal from the isoenzyme C on the thermal stability of the protein.