Does Urea Formation Have a Feedback Inhibition Mechanism - Assignment Example

” In urea cycle in case of birds and young mammals, arginine is not synthesized for protein synthesis because of “inborn errors of urea cycle enzymes” (Das 475), and it is produced with processes other than feedback mechanism. There is no feedback inhibition mechanism exhibited by urea formation during the urea cycle, at least not within the physiological concentration range. Carbomyl phosphate synthase I act as the rate-limiting enzyme in the urea cycle. N-acetylglutamate allosterically activates it thus lowering its Km for protein synthesis.

Carbomyl Phosphate Synthase I binds with the primary ATP molecule and converts into a vigorous confirmation. It then changes into a second form by binding with N-acetylglutamate thus enhancing its own ATP affinity. As a result, a phosphate group is transferred from a subsequent ATP to the enzyme-bound carbamate. This changes the carbamate to carbomyl phosphate. This happens according to the Rubio-Britton-Grisolia model. Hence, it is seen that hepatic N-acetylglutamate controls the rate of protein synthesis in the urea cycle, by regulating its rate-limiting enzyme allosterically (Das 475).

Arginine does not cause feedback inhibition of Carbomyl PS-1 or OTC but stimulates the activity of acetylglutamate synthetase.