Assays of ceruloplasmin vs myeloperoxidase: Witnessing the great battle, or mixing chalk and cheese?

Abstract

A paper in this issue [Panasenko et al., Biophysics 53 (4), 268 (2008)] furthers the idea of myeloperoxidase inhibition by ceruloplasmin, confirming the earlier reports with standard chlorination and peroxidase tests, and introducing a new version of the luminol chemiluminescence assay. However, there are outstanding discrepancies in the data on ceruloplasmin efficacy and their interpretation. In my opinion, they can be resolved only admitting that the supposedly equivalent assays register essentially different types of process, which involve the same chemical entities but on different spatiotemporal scales. The immediate flash caused by hydrogen peroxide in the myeloperoxidase/luminol/chloride mixture must reflect the non-equilibrium events within and/or at the surface of the enzyme molecule pre-loaded with the reactants. This phenomenon (which should perhaps be called “prompt chemiluminescence” in contrast to the much longer glow recorded in all usual assays and associated with secondary reactions in the bulk) is quite interesting in the biophysical aspect. It can be used for functional dissection of such multipathway, multilevel systems, and in particular, can indeed help clarify the situation concerning the putative ceruloplasmin control over myeloperoxidase.