title: Unusual Peroxide-Dependent, Heme-Transforming Reaction Catalyzed by HemQ.
abstract: A recently proposed pathway for heme b biosynthesis, common to diverse bacteria, has the conversion of two of the four propionates on coproheme III to vinyl groups as its final step. This reaction is catalyzed in a cofactor-independent, H2O2-dependent manner by the enzyme HemQ. Using the HemQ from Staphylococcus aureus (SaHemQ), the initial decarboxylation step was observed to rapidly and obligately yield the three-propionate harderoheme isomer III as the intermediate, while the slower second decarboxylation appeared to control the overall rate. Both synthetic harderoheme isomers III and IV reacted when bound to HemQ, the former more slowly than the latter. While H2O2 is the assumed biological oxidant, either H2O2 or peracetic acid yielded the same intermediates and products, though amounts significantly greater than the expected 2 equiv were required in both cases and peracetic acid reacted faster. The ability of peracetic acid to substitute for H2O2 suggests that, despite the lack of catalytic residues conventionally present in heme peroxidase active sites, reaction pathways involving high-valent iron intermediates cannot be ruled out.
authors.affiliation: †Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59715-3400, United States.
authors.forename: Arianna I
authors.initials: AI
authors.lastname: Celis
authors.affiliation: †Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59715-3400, United States.
authors.forename: Bennett R
authors.initials: BR
authors.lastname: Streit
authors.affiliation: †Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59715-3400, United States.
authors.forename: Garrett C
authors.initials: GC
authors.lastname: Moraski
authors.affiliation: †Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59715-3400, United States.
authors.forename: Ravi
authors.initials: R
authors.lastname: Kant
authors.affiliation: ‡Department of Chemistry, Illinois State University, Normal, Illinois 61790-4160, United States.
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Lash
authors.affiliation: §Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102-6050, United States.
authors.forename: Gudrun S
authors.initials: GS
authors.lastname: Lukat-Rodgers
authors.affiliation: §Department of Chemistry and Biochemistry, North Dakota State University, Fargo, North Dakota 58102-6050, United States.
authors.forename: Kenton R
authors.initials: KR
authors.lastname: Rodgers
authors.affiliation: †Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59715-3400, United States.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: DuBois
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D006418:Heme / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D010088:Oxidoreductases / Q000378:metabolism*; D010463:Peracetic Acid / Q000378:metabolism; D013211:Staphylococcus aureus / Q000201:enzymology* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D006418:Heme; D006861:Hydrogen Peroxide; D010088:Oxidoreductases; C402794:chlorite dismutase; D010463:Peracetic Acid