| Popis: |
The chlorination activity of free myeloperoxidase and myeloperoxidase bound with ceruloplasmin or with both ceruloplasmin and lactoferrin has been studied by luminal-dependent chemiluminescence. It was shown that the addition of hydrogen peroxide to the "myeloperoxidase + Cl- + luminal" system is accompanied by a fast flash of light emission. In the absence of myeloperoxidase or Cl-, the flash intensity was considerably reduced. The inhibitor of myeloperoxidase NaN3, the HOCl scavengers taurine and methionine, and guaiacol, a substrate for peroxidation cycle of myeloperoxidase, prevented luminescence. These results suggest that the generation of luminescence was due to the halogenating activity of myeloperoxidase, and hence, the flash light sum may serve as a measure of chlorination activity of myeloperoxidase. The activity of myeloperoxidase was suppressed by ceruloplasmin. Lactoferrin exhibited no significant influence on the myeloperoxidase activity, nor did it prevent the inhibitory effect of ceruloplasmin when they both were combined with myeloperoxidase. These data were confirmed using alternative approaches for evaluating the myeloperoxidase activity, namely, the assessment of peroxidation activity and the taurine chlorination assay. It is noteworthy that the inhibitory effect of ceruloplasmin on chlorination and peroxidation activities of myeloperoxidase is seen with the latter, traditional approaches only if ceruloplasmin is present in a large excess relative to myeloperoxidase, whereas the chemiluminescence method allows the detection of the inhibitory effect of ceruloplasmin using lower proportions of the protein with respect to myeloperoxidase, which are close to the stoichiometry of the myeloperoxidase/ceruloplasmin and the myeloperoxidase'ceruloplasmin'lactoferrin complexes. |
