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Preparation and properties of ferrous chloroperoxidase complexes with dioxygen, nitric oxide, and an alkyl isocyanide. Spectroscopic dissimilarities between the oxygenated forms of chloroperoxidase and cytochrome P-450.

1985; Elsevier BV; Volume: 260; Issue: 29 Linguagem: Inglês

10.1016/s0021-9258(17)36288-9

1083-351X

Masanori Sono, K S Eble, John H. Dawson, Lowell P. Hager,

bioluminescence and chemiluminescence research

Extensive spectroscopic investigations of chloroperoxidase and cytochrome P-450 have consistently revealed close similarities between these two functionally distinct enzymes.Although the CO-bound ferrous states were the first to display such resemblance, additional comparisons have focused on the native ferric and ferrous and the ligand-bound ferric derivatives of the enzymes.In order to test the extent to which the spectral properties of the two enzymes match each other, we have prepared the NO, alkyl isocyanide, and 0, adducts of ferrous chloroperoxidase, the latter two for the fiist time.As expected, the NO adducts of the two proteins have simlar UV-visible absorption and magnetic circular dichroism spectra; the same behavior is observed for the alkyl isocyanide complexes.Unexpectedly, the dioxygen adduct of ferrous chloroperoxidase (Le.Compound III), generated in cryogenic solvents at -30 OC by bubbling with 0 2 , is spectrally distinct from oxy-P-450-CAM.Identi~cation of this derivative as oxygenated chloroperoxidase is based on the following criteria: (a) It is EPR-silent at 77 K. (6)The bound 0 2 is dissociable as judged by the uniform conversion to the CO-bound form. (c) Oxy-chloroperoxidase autoxidizes to form the native ferric enzyme without detectable intermediates at a rate comparable to that determined for oxy-F-45O-~A~.Oxy-chloroperoxidase exhibits optical absorption (Aam (E-) = 354 (41), 430 (94), 554 (16.5), 587 (12.5)) and magnetic circular dichroism spectra that are clearly distinct from those of histidine-ligated heme proteins such as oxy-myoglobin or oxy-horseradish peroxidase.Sur-* This work was s u p p o ~ by Grants ~M-26730 (to J. €5.D.1 and