A chemical modification of myeloperoxidase and lactoperoxidase with 2-(O-methoxypolyethylene glycol)-4, 6-dichloro-s-triazine (activated PEG1).

The modification of myeloperoxidase and lactoperoxidase with 2-(O-methoxypolethylene glycol)-4, 6-dichloro-s-triazine, an activated polyethylene glycol (PEG1), was investigated. The modification caused a shift of the Soret band in the light absorption spectrum, from 430 nm to 418 nm in the case of myeloperoxidase (native ferric form), and from 412 nm to 406 nm in the case of lactoperoxidase (native ferric form). PEG1-modified myeloperoxidase and PEG1-modified lactoperoxidase both failed to bind with antiserum to the respective native enzyme, but both retained respectively 4.5 +/- 0.3 per cent (mean +/- SE, n = 5) and 0.6 +/- 0.2 per cent (mean +/- SE, n = 5) of the activities of peroxidation of the hydrogen donor o-methoxyphenol in comparison with the native enzyme, and 1.5 +/- 0.2 per cent (mean +/- SE, n = 5) and 1.2 +/- 0.2 per cent (mean +/- SE, n = 5) of the activities of destruction of fuchsin basic in the presence of hydrogen peroxide and a halide, bromide. The pH dependencies of the peroxidating activities were almost the same as those of the corresponding native enzymes, but both the optimal pHs of the reactions involving the destruction of fuchsin basic were shifted by approximately 1.0 pH unit toward neutral pH compared with the respective native enzymes.