Related Experiment Videos
Thyroxine deiodination associated with NADPH-dependent lipid peroxidation in a submicrosomal system
Summary
A peptide factor from liver microsomes drives lipid peroxidation, which oxidizes thyroxine. This process, involving malondialdehyde formation, shows thyroxine can inhibit its own deiodination.
Area of Science:
- Biochemistry
- Cell Biology
- Endocrinology
Background:
- Hepatic microsomes contain lipoproteins susceptible to oxidation.
- NADPH-dependent lipid peroxidation is a known cellular process.
- Thyroxine (T4) deiodination can occur under certain oxidative conditions.
Purpose of the Study:
- To characterize a factor that promotes microsomal lipid peroxidation.
- To investigate the relationship between lipid peroxidation and thyroxine deiodination.
- To elucidate the mechanism of thyroxine's interaction with lipid peroxidation.
Main Methods:
- Isolation of a peptide factor from hepatic microsomes via trypsin digestion and gel filtration (Sephadex G-100, G-25).
- In vitro oxidation system using NADPH, ferric ion-ADP complex, and NADPH-cytochrome c reductase.
- Measurement of malondialdehyde formation as an indicator of lipid peroxidation.
- Assay of thyroxine deiodination in the presence and absence of the peptide factor.
Main Results:
- A peptide mixture isolated from trypsin-treated microsomes significantly enhances lipid peroxidation.
- This enhanced lipid peroxidation system catalyzes the deiodination of thyroxine.
- Thyroxine itself inhibits the lipid peroxidation process as it undergoes deiodination.
Conclusions:
- A specific peptide factor from hepatic microsomes plays a crucial role in initiating lipid peroxidation.
- Lipid peroxidation is directly linked to the catalytic deiodination of thyroxine.
- Thyroxine exhibits feedback inhibition on the lipid peroxidation pathway it participates in.