Comparison of Some Enzyme Systems in Normal and Thyrotoxic Rat Livers

¹ From the Institute for Enzyme Research, University of Wisconsin, Madison, Wisconsin

The activity of the following enzymes and enzyme systems have been shown to increase above the normal in the mitochondria from thyrotoxic rats' livers: over-all glutamate oxidation, succinoxidase, cytochrome oxidase, cytochrome c, and adenosine triphosphatase. During hypothyroidism the activity of these enzymes decreases. Mg⁺⁺ ion concentration was not influenced by the thyroid hormone. The latent ATPase⁴ of thyrotoxic rat liver mitochondria is activated by shorter preaging periods at 37° than that of normal. In a whole homogenate of these same tissues the glucose-6-phosphatase activity, inorganic phosphate content and apparent protein level was also increased during thyrotoxicity.