Models for compound I of peroxidases and the oxygen-donating species in cytochrome P-450

292

A bstracts

F003 the

Models for Compound Species Oxygen-donating

I of Peroxidases in Cytochrome

.

D. Mandon a, B. Weu a, E. Bill b, C.H. Butzlaff Trautwein b K. Jayaraj c, A. Gold c, J. Ternerd s

and P-450 b,A. X.

aInstitut LeBel, UniversitC Louis Pasteur, Strasbourg Fr.; bInstitut Medizinische Universittit, Liibeck (FRG); ‘Department of fiir Physik, University of North Carolina at Environmental Sciences and Engineering, of Chemistry, Virginia Commonwealth Chapel Hill, NC USA; dDepartment I.Jniversity, V (USA);. IFe=OlO/i occur as intermediates in Ferryl-oxo porphyrin species the reaction of peroxidases and catalases with peroxide. Such species have in the catalytic cycle of also been postulated to occur as intermediates cytochrome c oxidase and as the oxygen donating species ir; cytochrome P450. Whereas, intermediates

the are,

structure and properties now, well established,

of the those

red ferryl-oxo of the green

IFelV==OI transients

IFe=Ol+, having incorporated a further oxidation equivalent, are, so far, less well understood. All these green intermediates are, presumably, ferryl-oxo a -cation radical complexes. However, the magnetic coupling between the cation radical and the ferryl-oxo unit is weak and of ambiguous sign in compound I of horseradish peroxidase (HRP-I)[ I], whereas, of intermediate strength and antiferromagnetic in compound I of chioropcroxidase (CPO1)[21. In contrast, a strong ferromagnetic coupling has been found in the oxidation product of iron XII complexes of tetra(mesityl)porphyrin (H2TMP)[3] and indications of a weak coupling of ambiguous sign has been obtained in transients formed by protonation of an iron II1 peroxo complex of “picket-fence“ porphyrin /4] Additional models for the green IFeIV=OI+ intermediates have, now, been generated using various porphyrins including tetra(a, u, a, a pivalamidophenyl)porphyrin (H2T(a,a,a,a-Ppiv)P ‘“picket-fence” porphyrin), tetra(a,p,a,p-pivalamidophenyl) porphyrin (HZT(a,B,tx,P-Ppiv) P and tetra(mcsity1) 2,3,7,X,12,13,17,18-octabromoporphyrin. (HzTMOBP). These transients have been characterized frequency R.R., EPR, and Mijssbauer susceptibility measurements. The results of

by UV-vis, spectroscopies these studies

IH

NMR, highand magnetic wili be presented.

1.C.E. Schulz, P.W. Devaney, H. Winkler, P.G. Debrunner,N. Doan, R. Rutter, L.P. Hager, FEBS Left., 103, 102 (1979). 2. R. Rutter, L.P, Hager, H. Dhonau, M.P. Hendrich, M. Valentine, P.G. Debrunner, Biochemiffry, 23, 6809 (1984). 3.B. Boso, 6. Lang, T.J. McMurry, J.T. Groves, .I. Chem.l>hys., 79, 1122 (1983). 4.D. Mandon, R. Weiss, E. Bill, M. Franke, A.X. Trautwein, Angew. Chem. Int. Ed. Engl, 28, 1709 (1989) R. Chiang,