Identification of a Porphyrin .pi. Cation Radical in Ascorbate Peroxidase Compound I

Biochemistry ◽  
1995 ◽  
Vol 34 (13) ◽  
pp. 4342-4345 ◽  
Author(s):  
William R. Patterson ◽  
Thomas L. Poulos ◽  
David B. Goodin
Keyword(s):  
Ascorbate Peroxidase ◽  
Cation Radical ◽  
Compound I

scholarly journals Scavenging of oxygen radicals by heme peroxidases.

1996 ◽  
Vol 43 (4) ◽  
pp. 673-678 ◽  
Author(s):  
L Gebicka ◽  
J L Gebicki
Keyword(s):  
Horseradish Peroxidase ◽  
Hydroxyl Radicals ◽  
Superoxide Radical ◽  
Cation Radical ◽  
Compound I ◽  
Superoxide Radical Anion ◽  
Form Compound ◽  
Activity Loss ◽  
Heme Peroxidases ◽  
Compound Ii

The reactions of two heme peroxidases, horseradish peroxidase and lactoperoxidase and their compounds II (oxoferryl heme intermediates, Fe(IV) = O or ferric protein radical Fe(III)R.) and compounds III (resonance hybrids [Fe(III)-O2-. Fe(II)-O2] with superoxide radical anion generated enzymatically or radiolytically, and with hydroxyl radicals generated radiolytically, were investigated. It is suggested that only the protein radical form of compound II of lactoperoxidase reacts with superoxide, whereas compound II of horseradish peroxidase, which exists only in oxoferryl form, is unreactive towards superoxide. Compound III of the investigated peroxidases does not react with superoxide. The lactoperoxidase activity loss induced by hydroxyl radicals is closely related to the loss of the ability to form compound I (oxoferryl porphyrin pi-cation radical, Fe(IV) = O(Por+.) or oxoferryl protein radical Fe(IV) = O(R.)). On the other hand, the modification of horseradish peroxidase induced by hydroxyl radicals has been reported to cause also restrictions in substrate binding (Gebicka, L. & Gebicki, J.L., 1996, Biochimie 78, 62-65). Nevertheless, it has been found that only a small fraction of hydroxyl radicals generated homogeneously does inactivate the enzymes.

scholarly journals A comprehensive test set of epoxidation rate constants for iron(iv)–oxo porphyrin cation radical complexes

2015 ◽  
Vol 6 (2) ◽  
pp. 1516-1529 ◽  
Author(s):  
Mala A. Sainna ◽  
Suresh Kumar ◽  
Devesh Kumar ◽  
Simonetta Fornarini ◽  
Maria Elisa Crestoni ◽  
...  
Keyword(s):  
Oxygen Atom ◽  
Gas Phase ◽  
Cation Radical ◽  
Compound I ◽  
Oxygen Atom Transfer ◽  
Test Set ◽  
Extensive Test ◽  
Comprehensive Test ◽  
First Time ◽  
Porphyrin Cation

Trends in oxygen atom transfer to Compound I of the P450 models with an extensive test set have been studied and show a preferred regioselectivity of epoxidation over hydroxylation in the gas-phase for the first time.

Models for peroxidase compound I: generation and spectroscopic characterization of new oxoferryl porphyrin .pi. cation radical species

1992 ◽  
Vol 31 (21) ◽  
pp. 4404-4409 ◽  
Author(s):  
D. Mandon ◽  
R. Weiss ◽  
K. Jayaraj ◽  
A. Gold ◽  
J. Terner ◽  
...  
Keyword(s):  
Cation Radical ◽  
Spectroscopic Characterization ◽  
Compound I ◽  
Radical Species

Defining substrate specificity and catalytic mechanism in ascorbate peroxidase

2004 ◽  
Vol 71 ◽  
pp. 27-38 ◽  
Author(s):  
Emma L. Raven ◽  
Latesh Lad ◽  
Katherine H. Sharp ◽  
Martin Mewies ◽  
Peter C. E. Moody
Keyword(s):  
Cytochrome C ◽  
Substrate Specificity ◽  
Ascorbate Peroxidase ◽  
Catalytic Mechanism ◽  
Cytochrome C Peroxidase ◽  
Structural Features ◽  
Organic Substrates ◽  
Class Iii ◽  
Compound I ◽  
Functional Features

Haem peroxidases catalyse the H2O2-dependent oxidation of a variety of, usually organic, substrates. Mechanistically, these enzymes are very well characterized: they share a common catalytic cycle that involves formation of a two-electron oxidized intermediate (Compound I) followed by reduction of Compound I by substrate. The substrate specificity is more diverse, however. Most peroxidases oxidize small organic substrates, but there are prominent exceptions to this and the structural features that control substrate specificity remain poorly defined. APX (ascorbate peroxidase) catalyses the H2O2-dependent oxidation of l-ascorbate and has properties that place it at the interface between the class I (e.g. cytochrome c peroxidase) and classical class III (e.g. horseradish peroxidase) peroxidase enzymes. We present a unified analysis of the catalytic and substrate-binding properties of APX, including the crystal structure of the APX-ascorbate complex. Our results provide new rationalization of the unusual functional features of the related cytochrome c peroxidase enzyme, which has been a benchmark for peroxidase-mediated catalysis for more than 20 years.

Sign in / Sign up

Export Citation Format

Share Document