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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
3
|
| pubmed:dateCreated |
1982-3-13
|
| pubmed:abstractText |
Horseradish peroxidase C (HRP; ferric) reacts with H2O2 to form Compound I, with an equilibrium constant of about 10(14) M-1. Two-step reduction of Compound I to Compound II and further to the ferric enzyme occurs reversibly at Eo' values of 0.90 and 0.93 V (pH 7.0), respectively. The pH dependence of Eo' values for each one-electron step, ferrous leads to ferric leads to Compound II leads to Compound I indicates that presence of redox-linked ionization at pKa values of 7.3 in the ferrous state, 11.0 in the ferric and 8.6 in Compound II. Zinc-substituted HRP C is oxidized to its free-radical form at an Eo' value of 0.74 (pH 6.0) Comparison of oxidized zinc HRP C with Compound I shows that Compound I contains a porphyrin pi-cation radical. The flash photolysis study on the NO-ferric HRP C complex clearly indicates that the iron is pentacoordinated in HRP C while it is hexacoordinated in metmyoglobin. From the kinetic analysis of the acid-alkaline conversion of HRP C, the second-order rate constants of the reactions with H+ and HO- are estimated to be 1.5 X 10(10) and 6.7 X 10(4) M-1s-1, respectively. The latter rate constant greatly varies with the kind of hemoproteins. In the presence of HRP C and O2, indole-3-acetate is oxidized to its hydroperoxide form, which reacts effectively with HRP C to form Compound I and further converts Compound I to a verdohemoprotein.
|
| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:chemical | |
| pubmed:status |
MEDLINE
|
| pubmed:month |
Nov
|
| pubmed:issn |
0300-8177
|
| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:day |
13
|
| pubmed:volume |
40
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
143-53
|
| pubmed:dateRevised |
2006-11-15
|
| pubmed:meshHeading |
pubmed-meshheading:7322114-Electron Transport,
pubmed-meshheading:7322114-Heme,
pubmed-meshheading:7322114-Horseradish Peroxidase,
pubmed-meshheading:7322114-Hydrogen-Ion Concentration,
pubmed-meshheading:7322114-Kinetics,
pubmed-meshheading:7322114-Oxidation-Reduction,
pubmed-meshheading:7322114-Peroxidases
|
| pubmed:year |
1981
|
| pubmed:articleTitle |
Horseradish peroxidase C.
|
| pubmed:publicationType |
Journal Article
|