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Equilibria between horseradish peroxidase and aromatic donors
Acta Chemica Scandinavica. Series B: Organic Chemistry and Biochemistry
|January 1, 1978
Summary
Horseradish peroxidase (HRP) binds aromatic donors to its protein, not iron. Binding affinity increases with larger aromatic systems, indicating specific protein interactions crucial for enzyme function.
Area of Science:
- Biochemistry
- Enzyme kinetics
- Protein-ligand interactions
Background:
- Horseradish peroxidase (HRP) is a key enzyme in various biological processes.
- Understanding the interaction between HRP and its substrates is crucial for elucidating its catalytic mechanisms.
Purpose of the Study:
- To investigate the binding equilibria between HRP and aromatic hydrogen donors.
- To determine the nature of the binding site and the factors influencing donor-enzyme affinity.
Main Methods:
- Spectrophotometric and potentiometric analyses were employed.
- Binding affinities (Kd) were determined for various aromatic donors.
- Enthalpy and entropy changes were calculated to characterize the binding interaction.
Main Results:
- Aromatic donors bind to the protein moiety of HRP, not the heme iron.
- Binding affinity is enhanced by larger pi-electron systems in the donors.
- Specific donor-enzyme interactions were indicated by negative entropy and enthalpy changes.
- Phenyl-Sepharose chromatography suggested involvement of aromatic amino acids in binding.
Conclusions:
- HRP-aromatic donor binding involves specific interactions with the enzyme's protein component.
- The heme iron and its redox state have minimal influence on donor binding.
- Plant peroxidases may exist in a donor-bound state in vivo.