The present study utilizes 1H NMR spectroscopy to characterize the binding of substrate to heme active site of three different peroxidases, horseradish peroxidase, lignin peroxidase, and manganese peroxidase. Information has been obtained on the site of p-cresol binding to the active-site cavity of the cyanide derivative of horseradish peroxidase. This information was obtained by relaxation enhancements of the substrate protons and connectivities between the latter and heme 8-CH3 and a Phe residue. Manganese-(II) is shown to bind to ferri-manganese peroxidase and its cyanide derivative in a specific site with a high-affinity constant (104 M−1) Manganese(II) binding exhibits a slow exchange rate with respect to the difference in T2−1 of the affected signals in the manganese(II)-containing and manganese(II)-free species. Manganese(II) affects the line width of certain heme methyl resonances and of certain one-proton intensity signals in manganese peroxidase and its cyanide derivative. The behavior of MnP toward manganese(II) is compared to that of the closely related peroxidase, lignin peroxidase (LiP), with its native substrate veratryl alcohol. LiP does not have a specific binding site for manganese(II).
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