Carbamyl Phosphate Synthetase Activity Research Articles

2-Acetoxyglutarate as an Activator of Carbamyl Phosphate Synthetase

2-Acetoxyglutarate as an Activator of Carbamyl Phosphate Synthetase

Citrulline synthesis in rat tissues

The distribution of carbamyl phosphate synthetase (CPS) and/or ornithine transcarbamylase (OTC) was determined in 17 different rat tissues. Both enzymes, but particularly OTC, were found to be located mainly in the liver so that assay for OTC activity can provide a highly specific test for liver parenchymal cells. Optimal conditions for treatment of small samples of liver to maintain enzyme activity on storage are described. The significance of the absence of detectable CPS activity in most tissues for the presumed role of carbamyl phosphate in pyrimidine biosynthesis is discussed. In addition, it was found that ( a) both CPS and OTC first appeared late in fetal life in the rat and did not reach adult levels until after birth, ( b) OTC activity in rat and mouse hepatomas varied from undetectable to the normal level of adult liver, and ( c) cells derived from liver and grown in culture were devoid of OTC activity.

Effect of thyroxine on enzymes of the urea cycle in regenerating rat liver.

SummaryThe activities of carbamyl phosphate synthetase, ornithine transcarbamylase and arginase have been found to be unchanged in regenerating liver of thyroidectomized rats. Complete thyroidectomy results in an impaired rate of liver regeneration. Daily injection of thyroxine during the regeneration period restores the capacity of the liver to regenerate.

Biochemical studies on amphibian metamorphosis. I. The effect of thyroxine on protein synthesis in the tadpole.

Thyroxine has been shown to accelerate the synthesis of carbamyl phosphate synthetase in the liver of Rana catesbeiana. Stimulation of carbamyl phosphate synthetase synthesis by thyroxine appears to be relatively specific because of the following observations: (1) succinoxidase activity decreased during the time that carbamyl phosphate synthetase increased; (2) liver catalase responded more slowly than carbamyl phosphate synthetase to thyroxine; (3) the ratio of biochemical changes/morphological changes was greatly altered during thyroxine-induced metamorphosis. The relationships between the concentration of thyroxine and (1) temperature; (2) duration of exposure of the tadpole to thyroxine; and (3) the activity of carbamyl phosphate synthetase during the induced synthesis of carbamyl phosphate synthetase by thyroxine are discussed. Chloramphenicol and thiouracil partly counteracted the effect of thyroxine on the synthesis of carbamyl phosphate synthetase.