Question

How does arginine regulate the urea cycle? If ↑[arginine] from dietary sources can enter the cycle, then why is it logical that arginine should have this effect?

Answer 1

The rate limiting step in urea cycle is formation of carbamoyl phosphate catalyzed by the enzyme, carbamoyl phosphate synthetase 1(CPS 1).a positive effector of this enzyme is N-acetyl glutamate(NAG).arginine os an activator of NAG synthase. So arginine enhances urea cycle.

If increased concentrations of arginine from food can enter urea cycle then inorder to metabolize this entering arginine, it must be hydrolyzed to produce urea, so urea cycle should be activated or enhanced which is done by the above mentioned action of arginine.