Carbamoyl phosphate synthetase I (CPS I) is a ligase enzyme located in the mitochondria involved in the production of urea.
In E. coli the single CPS that carries out the functions of CPSI and CPSII is a heterodimer with a small subunit and a larger subunit with about 382 and 1073 amino acid residues in size, although in mammals (and other vertebrates) the CPSI protein is encoded by a single gene.
[1] The small subunit contains one active site for the binding and deamination of glutamine to make ammonia and glutamate.
Urea can then be transferred back to the blood stream and to the kidneys for filtration and on to the bladder for excretion.
This is dangerous because ammonia is highly toxic to the body, especially the nervous system, and can result in intellectual disability and seizures.