Chicken kidney contains two arginases with different sedimentation coefficients and substrate specificity. The ligher of these arginases, which hydrolyses only L-arginine, has been purified about 3000-fold. Like the "ureotelic" arginase, developed in chicken liver after starvation, it displays many of the properties of the arginase of the "ureotelic" species. This seems to exclude the possibility that ureotelism and uricotelism are characterized by a specific type of arginases. Both liver and kidney arginases are located in the mitochondrial matrix. The rate of hydrolysis of arginine thus not only depends on the arginase activity but also on the rate of transport of arginine into the matrix. This last process therefore is of regulatory significance.
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