Analysis of the optical absorption and magnetic-circular-dichroism spectra of peanut peroxidase: electronic structure of a peroxidase with biochemical properties similar to those of horseradish peroxidase

Abstract

The electronic structures of the cationic isoenzyme of peanut peroxidase, horseradish peroxidase (isoenzyme C) and bovine liver catalase are compared through analysis of their optical absorption and magnetic c.d. (m.c.d.) spectral properties. The spectral data for the native resting states and compounds I and II of peanut peroxidase (PeP) are reported. The absorption and m.c.d. data for the native PeP exhibit bands characteristic of the high-spin ferric haem. The absorption spectrum of PeP compound I closely resembles that observed for the HRP compound I species. The m.c.d. data for PeP I clearly identifies that ring oxidation has occurred. One-electron reduction forms the PeP compound II species. The absorption and m.c.d. spectra recorded for PeP II exhibit the well-resolved spectral characteristics previously observed for both HRP compound II and catalase compound II. The spectral data of PeP with HRP and catalase are compared. The data clearly indicate that the m.c.d. spectral patterns of both plant peroxidases (PeP and HRP) are very similar and, therefore, the electronic structures of their resting states, and as well their primary and secondary compounds, must be similar. The m.c.d. data suggest that, while the compound I species of PeP and HRP belong to one electronic class, catalase compound I belongs to a different class. These data emphasize how the ground states of these two classes of oxidized haem, may be characterized as predominantly 2A2u (PeP I and HRP I) or 2A1u (catalase I). Peanut peroxidase is the second plant peroxidase for which the electronic structure of the compound I intermediate has been studied using the m.c.d. technique. The similarities with horseradish peroxidase allow us to suggest that plant peroxidases may operate by the same general mechanism, in spite of the low degree of sequence similarity between their polypeptide chains.

Delineating Heme-Mediated versus Direct Protein Oxidation in Peroxidase-Activated Cytochrome c by Top-Down Mass Spectrometry

“…It may seem counterintuitive that heme removal enhances the oxidation susceptibility of cyt c , considering the capability of metal centers to catalyze oxidation. ,,− However, metal catalysis is not the only factor that is relevant in this context. CD spectroscopy revealed that heme removal causes cyt c unfolding (Figure S4), confirming earlier reports that the protein structural integrity is contingent on heme .…”

“…Some protein oxidation events are catalyzed by transition metals. , Fenton-like reactions take place in the presence of peroxides, such as Fe­(II) + H 2 O 2 → Fe­(III) + • OH + OH – . Subsequent metal reduction regenerates Fe­(II) such that the process can continue, generating a steady supply of • OH radicals that attack the protein. ,, The peroxidase activity of some heme proteins represents another metal-catalyzed process. − In this case, H 2 O 2 reacts with Fe­(III) heme to form “Compound I”, an Fe­(IV)O species with an adjacent radical. The abstraction of hydrogen from R-H sites then regenerates Fe­(III) .…”

Comparative analysis of catalases: spectral evidence against heme‐bound water for the solution enzymes

“…2) [8]. It is also on the order of that observed for 5-coordinate horseradish and peanut peroxidases [20], although the Sorer MCD intensities of peroxidases are slightly more intense a factor we attribute to the strongly hydrogen-bonded histidine/histidinate 5th ligand (Andersson, L.A., in prep.). The Sorer MCD data for the three catalases are clearly considerably weaker in intensity than that typically observed for a 6-coordinate high-spin ferric heme, having water bound axially, of which metaquoMyoglobin is the best known example (e.g.…”

Online Detection of Peroxidase Using 3D Printing, Active Magnetic Mixing, and Spectra Analysis

“…The optical detection of the final catalysate has a close relation with the sensitivity of this proposed POD detection system [ 26 , 27 ]. The optical system consisted of three parts: (1) the optical detector (USB 4000, Ocean Optics, Dunedin, FL, USA) for collecting the absorption spectra of the final catalysate, (2) the LED light source with a power of 1 W for providing the incident light, and (3) the Z-type brown flow cell working as both the flow channel and the optical channel.…”