A Possible Function of Thiols, Including Glutathione, as Cofactors in the Conversion of Thyroxine to 3, 3, 5-Triiodothyronine in Rat Liver Microsomes

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概要

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• Thyroxine (T<SUB>4</SUB>) is known to be converted to triiodothyronine (T<SUB>3</SUB>) in rat liver microsomes. An endogenous stimulatory factor for the conversion of T<SUB>4</SUB> to T<SUB>3</SUB> was identified as reduced glutathione (GSH) by Sephadex G-15 gel chromatography of rat liver extract. The production of T<SUB>3</SUB> in rat liver microsomes was maximally stimulated above a GSH concentration of 4mm, and an approximately 5-fold stimulation was attained. This degree of stimulation was approximately 10 times less than that observed with dithiothreitol (DTT).<BR>Activity in the conversion of T<SUB>4</SUB> to T<SUB>3</SUB> was solubilized from the microsomes using 0.1% deoxycholate. When the solubilized microsomal preparation, pre-treated with DTT or GSH, was subjected to gel filtration on a Sepharose CL-6B column to separate the preparation from the thiol, almost no T<SUB>3</SUB> producing activity was observed in any of the collected fractions. However, when DTT or GSH was added to the fractions containing high molecular weight components, the activity of the production of T<SUB>3</SUB> was sustained. This finding indicates that these thiols play an essential role in the conversion of T<SUB>4</SUB> to T<SUB>3</SUB>, possibly acting as cofactors.

• 社団法人 日本内分泌学会の論文

著者

• Imai Yukihiro

  First Department Of Pathology Kobe University School Of Medicine

• Nishikimi Morimitsu

  Department Of Biochemistry Wakayama Medical University

• KATAOKA KUNITAKA

  First Department of Internal Medicine, Nagoya Universit School of Medicine

• IMAI YUKIHIRO

  First Department of Internal Medicine, Nagoya Uniuersity School of Medicine

• NISHIKIMI MORIMITSU

  Department of Medical Chemistry, Kochi Medical School

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