Peroxidase protein, reactivation

In view of the formation of a highly reactive Compound I ferryl species, and the fact that the porphyrin radical cation of this intermediate is reduced in enzymes such as CcP by a protein residue, it is not surprising that permanent covalent modifications are autocatalytically introduced into some protein frameworks. Two examples of autocatalytic protein modification, those of LiP and the catalase-peroxidases, are summarized here to illustrate the maturation of peroxidase protein structures that can have important functional consequences. 

The dioxygen-carrying proteins, hemoglobin and myoglobin, as well as the many synthetic model systems that have been developed recently,44 will not be considered here in this chapter since their chemistry is mainly that of iron in the + 2 oxidation state. The present chapter is therefore restricted to a brief description of the structure and reactivity of some cytochrome and peroxidase proteins. 

Figure 2 Potential relationships between NAD(P)H-derived ROS, redox systems, and signaling mechanisms regulated by PO2 in vascular smooth muscle. LDH, lactate dehydrogenase GSH red, glutathione reductase GSH Px, glutathione peroxidase RNS, reactive nitrogen species SOD, superoxide dismutases sGC, soluble guanylate cyclase MAPK, mitogen-activated protein kinases.

The attempts of Gjessing and Sumner (31) to reactive peroxidase protein by manganese protoporphyrin were criticized above (page 267). 

The reactivity of compounds such as 28 was clearly demonstrated by the peroxidase-catalyzed covalent binding of A -methyW-hydroxyellipticine (27) to proteins (756). Using horseradish peroxidase and hydrogen peroxide, tritiated-27 was converted to the 9-oxoellipticine derivative in the presence of bovine serum albumin (BSA) and human antibovine IgG in vitro. Covalent binding to these proteins was confirmed by gel electrophoresis, combustion, and liquid scintillation analysis. Dissolution of the BSA-ellipticinium derivative with pronase and... 

Several heme-containing proteins, including most peroxidases 12), have been observed to exhibit a low level of catalatic activity, with the chloroperoxidase from Caldariomyces fumago exhibiting the greatest reactivity as a catalase (13-15). Despite the fact that there is as yet only one such example to consider, it provides an alternate mechanism for the catalatic reaction and is addressed in this review. It was first characterized for its ability to chlorinate organic substrates in the presence of chloride and hydrogen peroxide at acid pH, but was later found... 

A number of NO-derived reactive species can initiate lipid peroxidation, including nitrogen dioxide and, most notably, ONOO , which displays unique properties as a mediator of lipid oxidation. On a molecular basis, ONOO is a more potent lipid oxidant than hydrogen peroxide and, unlike H2O2, it does not require metal catalysis. The one-electron oxidants such as metals, as well as heme proteins and peroxynitrite, are assumed to play an important role in many diseases associated with oxidative stress. Heme proteins such as horseradish peroxidase (HRP) can produce alkylperoxyl radicals through two sequential... 

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