ABSTRACT: We purified phosphate-independent glutaminases in liver and kidney to homogeneous proteins. The mode of activation of kidney enzyme caused some allosteric transition other than polymerization by maleate and unknown compound purified from kidney. Liver PIG displayed a typical sigmoidal velocity curve with respect to the substrate concentration and the sigmoidal curve was converted to a normal curve in the presence of activators (N-acetyl glutamate or maleate). This result provides evidence that the enzyme is polymerized in the presence of the substrate and the activators facilitate the polymerization of the enzyme. These activations may play a significant role in regulation of organ-specific glutamine metabolism.The fetal liver contains both the liver and kidney type glutaminases and also fetal kidney contains both the kidney and liver type enzymes. The kidney type enzyme in fetal liver was decreased gradually after birth, disappearing completely within one week. No kidney type enzyme was found in the regenerating liver in spite of its rapidly growing nature. From this evidence we offered our working hypothesis on the differentiation of organ characteristic isozyme.
Advances in Enzyme Regulation.