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Some basic properties of ascorbate-dependent antioxidative-defence factors from rat liver cytosol
1Institut für Physiologische Chemie I, Heinrich-Heine Universität Düsseldorf, Germany.
Chemico-Biological Interactions
|March 18, 1995
Summary
Two antioxidant factors (A and B) from rat liver cytosol were identified, inhibiting lipid peroxidation. Factor B, with a molecular mass of 60 kDa, showed greater stability and distinct properties compared to the larger Factor A (>400 kDa).
Area of Science:
- Biochemistry
- Cellular Biology
- Antioxidant Research
Background:
- Ascorbate (vitamin C) is a crucial water-soluble antioxidant.
- Lipid peroxidation is a damaging process implicated in various diseases.
- Rat liver cytosol contains factors that modulate antioxidant defense.
Purpose of the Study:
- To investigate the properties of ascorbate-dependent antioxidative-defense factors in rat liver cytosol.
- To characterize and differentiate two key inhibitory factors, designated A and B.
Main Methods:
- Ammonium sulfate fractionation and gel-filtration (Sephadex G-200, Sephacryl S-400) of rat liver cytosol.
- Assay of inhibitory capacity against Fe/ADP-ascorbate-induced lipid peroxidation.
- Analysis of factor properties including molecular mass, thiol dependency, ascorbate concentration effects, ionic strength, pH dependence, thermal stability, and sensitivity to ultrasonic treatment.
Main Results:
- Two distinct factors, A (>400 kDa) and B (60 kDa), were separated.
- Both factors required dithioerythritol for activity, with Factor B showing a stronger dependency.
- Factor B exhibited inhibitory activity at higher ascorbate concentrations than Factor A.
- Factor A's inhibitory capacity was significantly enhanced by increasing ionic strength, unlike Factor B.
- Factors A and B displayed different kinetics in inhibiting TBARS formation and chemiluminescence.
- Factor B was more thermostable and unaffected by freezing/thawing or sonication, while Factor A was inactivated by sonication.
Conclusions:
- Rat liver cytosol contains at least two distinct ascorbate-dependent antioxidant factors with differing molecular masses and biochemical properties.
- These factors likely facilitate the interaction of hydrophilic ascorbate with membrane-bound hydrophobic radicals, enhancing antioxidant defense.
- The distinct characteristics suggest specialized roles in protecting cellular components from oxidative damage.