The Effect of Thyroxine and Related Compounds on the Aerobic Myeloperoxidase - Catalysed Oxidation of NADH

Summary

Thyroxine concentrations as low as 1 μM significantly stimulate compound III formation during aerobic oxidation of NADH by highly purified myeloperoxidase. This increased compound III formation is parallelled by an increased oxidation of NADH. Stimulation by various thyronine and tyrosine analogues was in the order T₄ > T₃ > 3,5-T₂ (or triiodothyropropionic acid). Thyronine and diiodotyrosine had no significant effect. From the potencies of the various thyronines to stimulate compound III formation, the following structural features seem necessary:

(1) Substitution of thyronine with four iodine atoms.

(2) An amino group on the alanine side chain.

(3) Both aromatic rings of thyronine.

Key-Words

Myeloperoxidase - Aerobic Oxidation of NADH - Thyroxine - Compound