Oxidative Deamination of L-3:5:3′ Triiodothyronine by an Extract of Rat Kidney Mitochondria1

Publisher Website
Google Scholar
Abstract
The active enzyme catalizing the conversion of L-triiodothyronine to triiodothyroacetic acid has been prepared by repeated freezing and thawing of rat kidney mitochondria, centrifuging, and dialyzing the resulting supernatant. This preparation loses about 50% of its activity by heating at 56 C for 5 minutes. P-chloromercuribenzoate (1.3 × 10−4M) and anoxia are potent inhibitors of the converting enzyme. Cofactors such as FMN, FAD, DPN, α-ketoglutarate, pyruvate, ATP, pyridoxal phosphate, and the combination of α-ketoglutarate or pyruvate with pyridoxal phosphate have no significant effect on the activity of the converting enzyme. It has been found that the converting enzyme is about 1/7th as active as the crude untreated L-amino acid oxidase of cobra venom. Michaelis constant (Km) and Vmax of the converting enzyme, measured under specified conditions, are 3.25 × 10−5M and 85 mμ moles/mg N/hour, respectively.