Peroxidase-type reactions suggest a heterolytic/nucleophilic O-O joining mechanism in the heme-dependent chlorite dismutase.

ABSTRACT: Heme-containing chlorite dismutases (Clds) catalyze a highly unusual O-O bond-forming reaction. The O-O cleaving reactions of hydrogen peroxide and peracetic acid (PAA) with the Cld from Dechloromonas aromatica (DaCld) were studied to better understand the Cl-O cleavage of the natural substrate and subsequent O-O bond formation. While reactions with H2O2 result in slow destruction of the heme, at acidic pH heterolytic cleavage of the O-O bond of PAA cleanly yields the ferryl porphyrin cation radical (compound I). At alkaline pH, the reaction proceeds more rapidly, and the first observed intermediate is a ferryl heme. Freeze-quench EPR confirmed that the latter has an uncoupled protein-based radical, indicating that compound I is the first intermediate formed at all pH values and that radic

SUBMITTER: Mayfield JA 

PROVIDER: S-EPMC4390081 | biostudies-literature | 2013 Oct

REPOSITORIES: biostudies-literature