Abstract
In view of the role ascribed to the peroxidatic activity of degradation products of cytochrome c (cyt c) in the processes of apoptosis, we investigate the catalytic potential of heme and of the cyt c derived heme peptide MP-11 to catalyse the cathodic reduction of hydrogen peroxide and to oxidize aromatic compounds. In order to check whether cyt c has an enzymatic activity in the native state where the protein matrix should suppress the inherent peroxidatic activity of its heme prosthetic group, we applied a biocompatible immobilization matrix and very low concentrations of the co-substrate H2O2. The biocatalysts were entrapped on the surface of a glassy carbon electrode in a biocompatible chitosan layer which contained gold nanoparticles. The electrochemical signal for the peroxide reduction is generated by the redox conversion of the heme group, whilst a reaction product of the substrate oxidation is cathodically reduced in the substrate indication. The catalytic efficiency of microperoxidase-11 is sufficient for sensors indicating HRP substrates, e.g., p-aminophenol, paracetamol and catechol, but also the hydroxylation of aniline and dehalogenation of 4-fluoroaniline. The lower limit of detection for p-aminophenol is comparable to previously published papers with different enzyme systems. The peroxidatic activity of cyt c immobilized in the chitosan layer for catechol was found to be below 1 per mill and for p-aminophenol about 3% as compared with that of heme or MP-11.
Highlights
Cytochrome c is one of the best structurally characterized proteins
In view of the role that the peroxidatic activity of degradation products of cyt c may play in the processes of neurodegeneration or apoptosis, we investigate the potential of cyt c, of its prosthetic group hemin and of the cyt c derived heme peptide MP-11 to oxidize aromatic compounds, e.g., p-aminophenol, catechol, aniline and paracetamol
We published data about direct electron transfer of MP-11 on AuNP-CH/glassy carbon electrodes (GCEs) where chitosan capped gold nanoparticles were prepared in one step using chitosan as both reductant and stabilizer [14]
Summary
Cytochrome c is one of the best structurally characterized proteins. It was one of the first globular proteins whose crystal structure was determined. For the early stage of neurodegeneration, it is postulated that cyt c is released from dysfunctional mitochondria into the cytosol where it is converted to heme peptides by cytosolic proteases They may at least in part be responsible for the oxidative reactions of neurodegenerative diseases such as Parkinson’s disease, Alzheimer’s disease and amyotrophic lateral sclerosis. In view of the role that the peroxidatic activity of degradation products of cyt c may play in the processes of neurodegeneration or apoptosis, we investigate the potential of cyt c, of its prosthetic group hemin and of the cyt c derived heme peptide MP-11 to oxidize aromatic compounds, e.g., p-aminophenol, catechol, aniline and paracetamol
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