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The influence of the peptide chain on the kinetics and stability of microperoxidases
J H Spee1, M G Boersma, C Veeger
1Department of Biochemistry, Agricultural University, Wageningen, The Netherlands.
Abstract:
Microperoxidases with increasing lengths of the peptide attached to the heme moiety have been isolated after proteolytic digestion of horse-heart cytochrome c (microperoxidases 6, 8, and 11) and of cytochrome c550 from Thiobacillus versutus (microperoxidase 17). The different microperoxidases catalyze the H2O2-dependent para-hydroxylation of aniline relatively efficiently but are rapidly inactivated under turnover conditions. The horse-heart cytochrome-c-derived microperoxidases have identical values for Vmax but show a decrease of the K(m) for aniline and a higher stability when the attached peptide is longer. The kinetic constants obtained for microperoxidase 17, differ markedly from the microperoxidases derived from horse-heart cytochrome c. Possible factors underlying the observed differences are discussed.
Insights
Researchers studied microperoxidases derived from cytochrome c, finding longer peptide chains enhance aniline hydroxylation efficiency and stability. However, microperoxidase 17 showed distinct kinetic properties compared to others.
Area of Science:
- Biochemistry
- Enzymology
- Protein Chemistry
Background:
- Cytochrome c and its derivatives, microperoxidases, are heme-containing proteins.
- Microperoxidases are studied for their catalytic activities, particularly in oxidation reactions.
- Understanding structure-activity relationships is crucial for enzyme engineering.
Purpose of the Study:
- To investigate the catalytic activity and stability of microperoxidases with varying peptide lengths.
- To compare microperoxidases derived from horse-heart cytochrome c with microperoxidase 17.
- To elucidate the impact of peptide chain length on kinetic parameters and enzyme stability.
Main Methods:
- Proteolytic digestion of horse-heart cytochrome c and Thiobacillus versutus cytochrome c550 to isolate microperoxidases.
- Assay of H2O2-dependent para-hydroxylation of aniline.
- Kinetic analysis to determine Vmax and K(m) values.
- Assessment of enzyme stability under turnover conditions.
Main Results:
- Microperoxidases 6, 8, and 11 (from horse-heart cytochrome c) and microperoxidase 17 (from T. versutus cytochrome c550) were isolated.
- All microperoxidases efficiently catalyzed aniline para-hydroxylation but showed rapid inactivation.
- Horse-heart cytochrome c-derived microperoxidases exhibited identical Vmax, decreased K(m) for aniline, and increased stability with longer peptides.
- Microperoxidase 17 displayed significantly different kinetic constants compared to horse-heart cytochrome c-derived microperoxidases.
Conclusions:
- Peptide length significantly influences the kinetic properties and stability of microperoxidases derived from horse-heart cytochrome c.
- Microperoxidase 17 possesses distinct characteristics, suggesting structural or functional differences.
- Further investigation is needed to understand the factors contributing to these observed differences in microperoxidase activity and stability.