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Updated: Jul 22, 2026
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Isolation and Biophysical Study of Fruit Cuticles
Published on: March 30, 2012
1H-NMR characterization of cucumber peroxidases
L B Dugad1, H M Goff, F B Abeles
1Department of Chemistry, University of Iowa, Iowa City 52242.
Biochimica Et Biophysica Acta
|December 11, 1991
Summary
Cucumber seedlings contain two unique peroxidase isoenzymes. Proton NMR spectroscopy revealed distinct heme environments and confirmed the acidic form is monomeric, not dimeric.
Area of Science:
- Biochemistry
- Plant Science
- Spectroscopy
Background:
- Peroxidases are crucial enzymes in plants.
- Cucumber seedlings possess acidic and basic peroxidase isoenzymes.
- Previous characterization of the acidic isoenzyme suggested it was dimeric.
Purpose of the Study:
- To characterize two cucumber peroxidase isoenzymes using 1H-NMR spectroscopy.
- To elucidate the heme active site environments of these isoenzymes.
- To re-evaluate the quaternary structure of the acidic isoenzyme.
Main Methods:
- Proton Nuclear Magnetic Resonance (1H-NMR) spectroscopy.
- Characterization of native (ferric high-spin) and cyanide-ligated (ferric low-spin) forms.
- Comparison with horseradish peroxidase C (HRP(C)) spectra.
Main Results:
- Both cucumber peroxidases possess a protohemin IX prosthetic group with proximal histidine.
- Distinct heme 1H-NMR shift patterns indicate different active site environments.
- The acidic isoenzyme exists as a 30 kDa monomer, contrary to prior dimeric (60 kDa) characterization.
- The basic isoenzyme exhibits less heme signal asymmetry than the acidic isoenzyme or HRP(C).
Conclusions:
- Cucumber peroxidases share structural similarities with HRP(C) regarding the heme prosthetic group.
- Subtle differences in heme environments exist between the acidic and basic cucumber peroxidases.
- The acidic cucumber peroxidase is predominantly monomeric in solution.
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