Spectroscopic evidence of the effect of hydrogen peroxide excess on the coproheme decarboxylase from actinobacterial .

The actinobacterial coproheme decarboxylase from catalyzes the final reaction to generate heme via the "coproporphyrin-dependent" heme biosynthesis pathway in the presence of hydrogen peroxide. The enzyme has a high reactivity toward HO used for the catalytic reaction and in the presence of an excess of HO new species are generated. Resonance Raman data, together with electronic absorption spectroscopy and mass spectrometry, indicate that an excess of hydrogen peroxide for both the substrate (coproheme) and product (heme ) complexes of this enzyme causes a porphyrin hydroxylation of ring C or D, which is compatible with the formation of an iron chlorin-type heme species.

An active site at work - the role of key residues in C. diphteriae coproheme decarboxylase.

Coproheme decarboxylases (ChdCs) are utilized by monoderm bacteria to produce heme b by a stepwise oxidative decarboxylation of the 2- and 4-propionate groups of iron coproporphyrin III (coproheme) to vinyl groups. This work compares the effect of hemin reconstitution versus the hydrogen peroxide-mediated conversion of coproheme to heme b in the actinobacterial ChdC from Corynebacterium diphtheriae (CdChdC) and selected variants. Both ferric and ferrous forms of wild-type (WT) CdChdC and its H118A, H118F, and A207E variants were characterized by resonance Raman and UV-vis spectroscopies.