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Summary
Beef peroxidase activity was separated into five fractions using DEAE-cellulose chromatography. The most active fraction, purified to 59,000-fold, showed enhanced enzymatic rates but limited stability, suggesting proteolysis conditions influence molecular size.
Area of Science:
- Biochemistry
- Enzymology
Background:
- Peroxidase activity in beef subcellular particles is crucial for various biological processes.
- Previous studies on trypsin-solubilized thyroid peroxidase reported varying molecular sizes, indicating potential complexities in enzyme characterization.
Purpose of the Study:
- To resolve and characterize the peroxidase activity from beef subcellular particles.
- To investigate the influence of purification methods on enzyme activity and stability.
- To compare the properties of purified beef peroxidase with other known peroxidases.
Main Methods:
- DEAE-cellulose chromatography to resolve peroxidase fractions.
- Hydroxylapatite chromatography for further purification of active components.
- Gel filtration and absorbance measurements for molecular size and purity determination.
- Enzymatic assays to measure iodide and guaiacol oxidation rates.
Main Results:
- Five distinct peroxidase fractions were obtained, with molecular sizes ranging from 73,000 to 340,000 daltons.
- The most active fraction (92,000 daltons) was purified 59,000-fold, exhibiting significantly higher catalytic rates for iodide and guaiacol oxidation compared to previous preparations.
- This highly purified enzyme showed decreased stability and a reduced guaiacol to iodide activity ratio, and its turnover numbers were comparable to commercial lacto- and horseradish peroxidases.
- Other fractions contained less active and more stable peroxidase components, with molecular sizes of 73,000-340,000 daltons.
- The pH optima for iodide oxidation varied, while guaiacol oxidation optima were similar across different peroxidases.
Conclusions:
- The molecular size of trypsin-solubilized thyroid peroxidase is significantly influenced by proteolysis conditions.
- Purification of beef peroxidase leads to increased specific activity but reduced stability.
- The kinetic properties of the purified beef peroxidase are similar to those of lacto- and horseradish peroxidases, suggesting conserved functional mechanisms.