Urea cycle · reaction 1 of 5

Ammonia + Carbon dioxide + 2 ATP + Water → Carbamoyl phosphate + 2 ADP + Inorganic phosphate

Carbamoyl phosphate synthetase I EC 6.3.4.16

Captures free ammonia and fixes it into a stable molecule, spending two ATP. It is the step that commits the nitrogen to urea and the one that sets the pace of the cycle.

irreversible
Mitochondrial matrix

in depth

ΔG°′: not documented
Location: Mitochondrial matrix

Fun fact

It only works if N-acetylglutamate is present, a molecule made when glutamate is abundant. In other words: the cycle switches on only when there is surplus nitrogen to get rid of.

Nelson, D. L. & Cox, M. M. (2021). Lehninger. Principios de bioquímica, 8.ª ed., ch. 18

previousnext

Overview Pathways Minigames

Urea cycleCarbamoyl phosphate synthetase I

100 %

esc

↑↓ navigate · ↵ open · esc close