Resonance Raman evidence for Fe(IV) in compound II of horseradish peroxidase

The syntheses of the [Cat]3[Fe&,L6] clusters (L = Br-, cat = [Et3MeN]'; L = A S , Cat = [Et4N]+) are reported. The crystal and molecular structures of [Et4N]3[Fe6S6@-CH3C6H40)6] (I) and of [Et4NI3[Fe6S6Br6].CH,CN (11) are described in detail. I and I1 crystallize in the monoclinic space groups P2,/a and P2,/n, respectively, with two molecules in the unit cell. The cell dimensions in I are a = 13.173 (5) A, b = 19.848 (10) A, c = 14.304 (4) A, and 0 = 98.05 (3)O. In 11, a = 14.531 (3) A, b = 11.028 (2) A, c = 17.566 (3) A, and 0 = 100.69 (1)'. Intensity data for both I and I1 were collected with a four-circlecomputer-controlled diffractometer with use of the 8-28 scan technique. Both structures were solved by conventional methods from 3461 and 2516 reflections for I and 11, respectively. The structures were refined by full-matrix least-squares techniques (283 parameters for I and 213 parameters for 11) to final R values of 0.075 and 0.049, respectively, for I and 11. The anions in I and I1 contain the [Fe6s613* hexagonal-prismatic core, which consists of alternating tetrahedral Fe and triply bridging S atoms. Three of the Fe coordination sites are occupied by core sulfide atoms while the fourth coordination site is filled by the terminal ROand Brligands. There are two sets of Fee-Fe distances in the Fe6S6 cores with mean values of 2.761 ( 5 ) , 2.749 (4) A and 3.80 (4), 3.81 (2) A, respectively, for I and 11. Similarly, two sets of Fe-S-Fe angles are found for I and I1 at 74.6 (2) and 74.3 (1)O and 113.8 (2) and 114.2 (9)'. The Fe-S bonds in I and I1 are 2.276 (5) and 2.274 (4) A. The Fe-O bond in I is 1.880 (1 1) A, and the Fe-Br bond in I1 is 2.366 (9) A. The reactivity, cyclic voltammetry, and isotropically shifted N M R spectra of I and I1 are discussed in detail.-

show abstract

“…A table of anisotropic temperature factors has been deposited. 4 Calculated standard deviations are indicated in parentheses.…”

Section: Resultsmentioning

confidence: 99%

“…The Fe-Br distance in II at 2.366 (9) A (range 2.351 (2)-2.382 (2) A) is comparable to the Fe-Br distance in [Fe4S4(Br)4]2' at 2.341 (2) A.28 The Br-Fe-S angles in II also are similar to the cubane homologue and range from 110. 4 (1) to 113. 5 (1)°.…”

Section: Resultsmentioning

confidence: 99%

Chemistry of iron-sulfido [Fe6S6]3+ prismatic cages. Synthesis, structural characterization, and electronic structures of the [Et4N]3[Fe6S6L6] clusters (L = p-CH3C6H4O-, Br-)

1986

View full text Add to dashboard Cite

show abstract

“…This intermediate has a formal oxidation state of IV. Mossbauer (Schultz et al, 1984) and resonance Raman (Rakhit et al, 1976;Felton et al, 1976;Terner & Reed, 1984) spectroscopies indicate an FeIV=O structure for H R P compound 11. Recent resonance Raman evidence also suggests an FeTV=O structure for Lip compound 11 (Anderson et al, 1987).…”

Section: Discussionmentioning

confidence: 99%

Manganese peroxidase from the basidiomycete Phanerochaete chrysosporium: spectral characterization of the oxidized states and the catalytic cycle

Wariishi

Akileswaran²,

Gold³

1988

Biochemistry

298

219

View full text Add to dashboard Cite

Manganese peroxidase (MnP), an extracellular heme enzyme from the lignin-degrading fungus Phanerochaete chrysosporium, catalyzes the Mn(II)-dependent oxidation of a variety of phenols. Herein, we spectroscopically characterize the oxidized states of MnP compounds I, II, and III and clarify the role of Mn in the catalytic cycle of the enzyme. Addition of 1 equiv of H2O2 to the native ferric enzyme yields compound I, characterized by absorption maxima at 407, 558, 605, and 650 nm. Addition of 2 or 250 equiv of H2O2 to the native enzyme yields compound II or III, respectively, identified by absorption maxima at 420, 528, and 555 nm or at 417, 545, and 579 nm, respectively. These characteristics are very similar to those of horseradish peroxidase (HRP) and lignin peroxidase (LiP) compounds I, II, and III. Addition of 1 equiv of either Mn(II), ferrocyanide, or a variety of phenols to MnP compound I rapidly reduces it to MnP compound II. In contrast, only Mn(II) or ferrocyanide, added at a concentration of 1 equiv, reduces compound II. The Mn(III) produced by the enzymic oxidation of Mn(II) oxidizes the terminal phenolic substrates. This indicates that compounds I and II of MnP contain 2 and 1 oxidizing equiv, respectively, over the native ferric resting enzyme and that the catalytic cycle of the enzyme follows the path native enzyme----compound I----compound II----native enzyme. In addition, these results indicate that Mn(II) serves as an obligatory substrate for MnP compound II, allowing the enzyme to complete its catalytic cycle. Finally, the Mn(II)/Mn(III) redox couple enables the enzyme to rapidly oxidize the terminal phenolic substrates.

show abstract

“…Much effort has gone into separating these parameters and a classification of haem proteins on the basis of spin state and oxidation state has appeared recently (Spiro & Burke, 1976). Although the framework for using spin and oxidation state markers exists some revision of earlier classifications has been necessary and further additions and modifications may be needed (Champion et al 19766;Rakhit, Spiro & Uyeda, 1976;Champion & Gunsalus, 1977).…”

Section: Structure (Spin and Oxidation State) Markersmentioning

confidence: 99%

Resonance Raman spectroscopy in biochemistry and biology

Carey

1978

Quart. Rev. Biophys.

View full text Add to dashboard Cite

Resonance Raman (RR) spectroscopy provides detailed information on the vibrational and electronic properties of biochemical and biological chromophores. The analysis of RR spectra, using for example model compounds or a group frequency approach, enables us to form an accurate structural picture of the chromophore in its natural biological site. Moreover, the insight gained into the electronic states of a biological chromophore can be crucial to our understanding of its function. Thus the RR technique represents a powerful means of eliciting precise structural and electronic data from a coloured species and of focusing upon key aspects of its function. It has even been possible to obtain RR spectra from some natural chromophores in vivo, giving spectra detailed and informative enough to please a spectroscopist from a system complex enough to satisfy a biologist.

show abstract

Resonance Raman evidence for Fe(IV) in compound II of horseradish peroxidase

Cited by 54 publications

References 18 publications

Chemistry of iron-sulfido [Fe6S6]3+ prismatic cages. Synthesis, structural characterization, and electronic structures of the [Et4N]3[Fe6S6L6] clusters (L = p-CH3C6H4O-, Br-)

Chemistry of iron-sulfido [Fe6S6]3+ prismatic cages. Synthesis, structural characterization, and electronic structures of the [Et4N]3[Fe6S6L6] clusters (L = p-CH3C6H4O-, Br-)

Manganese peroxidase from the basidiomycete Phanerochaete chrysosporium: spectral characterization of the oxidized states and the catalytic cycle

Resonance Raman spectroscopy in biochemistry and biology

Contact Info

Product

Resources

About