Comparison of heme environments and proximal ligands in peroxidases and other hemoproteins through carbon-13 nuclear magnetic resonance spectroscopy of carbon monoxide complexes

Carbon-13 nuclear magnetic resonance signals for the carbon monoxide ligand in ferrous complexes of horseradish peroxidase, lactoperoxidase, and chloroperoxidase are located respectively at 209.1, 208.3, and 200.8 parts per million from the tetramethylsilane reference. On the basis of previous hemoprotein and model compound studies these resonance positions are consistent with coordination of a proximal histidine ligand in horseradish peroxidase and lactoperoxidase, and coordination of a cysteinyl mercaptide ligand in chloroperoxidase. Carbonyl chemical shift values for acidic and basic horseradish peroxidase isoenzymes are very similar.