Thyroxine Deiodination Associated with NADPH-Dependent (Enzymatic) and Fe 3+ -ADP-Catalyzed (Nonenzymatic) Reactions in Hepatic Microsomes

Abstract

Summary

Oxidative degradation of phospholipid in rat liver microsomes accompanied by degradation of added thyroxine can be effected in at least two different systems. One of these is NADPH-dependent (enzymatic) and the other is Fe³⁺-ascorbate-dependent (nonenzymatic). Ascorbate can replace the NADPH as the substrate in the enzyme-catalyzed reaction.

In addition, the ferric iron-adenosine diphosphate complex, which serves as a catalyst in the NADPH-dependent lipid peroxidation, can also in the presence of rat liver microsomes catalyze thyroxine degradation without lipid peroxidation.