Oxygen exchange with water in heme-oxo intermediates during H2O2-driven oxygen incorporation in aromatic hydrocarbons catalyzed by microperoxidase-8.
The present paper describes the oxygen incorporation into naphthalene and anthracene by H2O2-driven microperoxidase-8, forming alpha-naphthol and anthraquinone, respectively. Microperoxidase-8 is a minienzyme containing a histidinyl-coordinated Fe3+-protoporphyrin IX cofactor covalently attached to an eight-amino-acid peptide. Additional experiments were performed to investigate whether the reaction mechanism involved is like that of peroxidase and/or cytochrome P-450. A reaction pathway like that of cytochrome P-450 implies oxygen transfer to the substrate from the as yet uncharacterized iron-oxo species formed in the reaction of the heine cofactor with H2O2. In contrast, a peroxidase-type reaction chemistry involves reaction pathways proceeding by initial one-electron oxidation of, or H-abstraction from, the substrate, followed by incorporation of oxygen from sources other than the iron-oxo species, i.e. from other than H2O2. The results of the present study exclude Fenton-type chemistry and prove that the minicatalyst is able to catalyze the oxygen incorporation by both peroxidase and cytochrome P-450 types of reaction pathways, while exchange occurs between the high-valency iron-oxo species and H2O. The mechanistic implications of this exchange for cytochrome P-450 are discussed.
Dorovska-Taran
V
V
Department of Biochemistry, Agricultural University, Wageningen, The Netherlands.
Posthumus
M A
MA
Boeren
S
S
Boersma
M G
MG
Teunis
C J
CJ
Rietjens
I M
IM
Veeger
C
C
D000818:Animals; D000873:Anthracenes / Q000378:metabolism*; D001554:Benzene / Q000378:metabolism*; D002384:Catalysis; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D003574:Cytochrome c Group / Q000737:chemistry / Q000378:metabolism; D006736:Horses; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D008956:Models, Chemical; D009281:Naphthalenes / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013379:Substrate Specificity; D014867:Water
D000873:Anthracenes; D003574:Cytochrome c Group; D009281:Naphthalenes; D014867:Water; C031721:naphthalene; D003577:Cytochrome P-450 Enzyme System; D006861:Hydrogen Peroxide; D010544:Peroxidases; C021799:microperoxidase; D001554:Benzene; D010100:Oxygen