Asparagine metabolism in chicks and rats

Asparaginase and asparagine synthetase specific activity (enzyme units/mg protein) was determined in chicks and rats fed various protein diets. The specific activity of asparaginase was twofold higher in the kidney compared to the liver of chicks fed a 25% protein control diet, whereas the specific activity of asparaginase was eightfold greater in the liver compared to kidney tissue of rats fed the 25% protein control diet. The asparaginase specific activity in the chick liver, chick kidney, and rat liver were all significantly increased when animals were fed the 75% protein diet. Asparaginase specific activity increased significantly in rat and chick kidneys when the animals were fasted. Dietary supplementation of asparagine did not significantly increase asparaginase specific activity in either animal. The combined kidney and liver asparagine synthetase specific activity for chicks fed the control diets is over seven hundred times less than the corresponding combined asparaginase specific activity. Rats fed the control diet had a combined kidney and liver asparagine synthetase specific activity about 75 times less than the corresponding asparaginase specific activity. The asparagine synthetase specific activity was significantly increased in the rat and chick kidney when a 2% protein diet was fed.