Which among the following is the rate limiting enzyme in urea synthesis?
Carbamoyl phosphate synthetase I which catalyse the condensation of CO2, ammonia, and ATP to form carbamoyl phosphate is the rate limiting enzyme in urea synthesis. It is active only in the presence of N-acetylglutamate, which is an allosteric activator that enhances the affinity of the synthase for ATP. Some reactions of urea cycle occur in the mitochondria and some occur in the cytoplasm. Synthesis of 1 mol of urea requires 3 mol of ATP, 1 mol each of ammonium ion and of aspaate, and employs five enzymes. Ref: Rodwell V.W. (2011). Chapter 28. Catabolism of Proteins & of Amino Acid Nitrogen. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.
Argininosuccinate lyase
Argininosuccinate synthase
Ornithine transcarbamoylase
Carbamoyl phosphate synthetase I