Pyrimidines · reaction 1 of 6

Glutamine + Carbon dioxide + 2 ATP + Water → Carbamoyl phosphate + Glutamate + 2 ADP + Inorganic phosphate

Carbamoyl phosphate synthetase II EC 6.3.5.5

Makes carbamoyl phosphate just like the urea cycle enzyme, but in the cytosol and taking the nitrogen from glutamine instead of free ammonia. Two enzymes, two compartments and two fates for the same molecule.

irreversible
Cytosol

in depth

ΔG°′: not documented
Location: Cytosol

Fun fact

The cell keeps the two pools of carbamoyl phosphate apart because it does not want nitrogen meant for disposal to be diverted into making DNA. The mitochondrial membrane is what enforces the separation.

Nelson, D. L. & Cox, M. M. (2021). Lehninger. Principios de bioquímica, 8.ª ed., ch. 22

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PyrimidinesCarbamoyl phosphate synthetase II

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