Reaction of N-hydroxyguanidine with the ferrous-oxy state of a heme peroxidase cavity mutant: a model for the reactions of nitric oxide synthase.

ABSTRACT: Yeast cytochrome c peroxidase was used to construct a model for the reactions catalyzed by the second cycle of nitric oxide synthase. The R48A/W191F mutant introduced a binding site for N-hydroxyguanidine near the distal heme face and removed the redox active Trp-191 radical site. Both the R48A and R48A/W191F mutants catalyzed the H2O2 dependent conversion of N-hydroxyguanidine to N-nitrosoguanidine. It is proposed that these reactions proceed by direct one-electron oxidation of NHG by the Fe(+4)O center of either Compound I (Fe(+4)=O, porph+(.)) or Compound ES (Fe(+4)=O, Trp+(.)). R48A/W191F formed a Fe(+2)O2 complex upon photolysis of Fe(+2)CO in the presence of O2, and N-hydroxyguanidine was observed to react with this species to produce products, distinct from N-nitrosoguanidine, that

SUBMITTER: Nigro AP 

PROVIDER: S-EPMC2902621 | biostudies-literature | 2010 Aug

REPOSITORIES: biostudies-literature