Isolation from bovine spleen of a green heme protein with properties of myeloperoxidase.

A novel green heme protein from bovine spleen has been purified to apparent homogeneity. The visible spectrum, with unusually long wavelength absorptions due to alpha-, beta-, and gamma-porphyrin bands, the EPR g values of 6.81, 4.99, and 1.94, and the peroxidase activity are similar to those of myeloperoxidase (EC 1.11.1.7). The observed molecular mass of 57,000 daltons (established by gel permeation chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis studies) clearly distinguishes it from myeloperoxidase, as does the observed substrate specificity (e.g. oxidation of iodide but not ascorbate). Optical spectra of ferric and ferrous forms of the enzyme in the native state, complexed with ligands (CN-, CO, NO, N3-) and as the pyridine hemochromogens, are presented and compared to those of the corresponding derivatives of myeloperoxidase.