Carbamoyl phosphate synthetase I
carbamoyl-phosphate synthetase 1, mitochondrial | |||||||
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Identifiers | |||||||
Symbol | CPS1 | ||||||
Chr. 2 p | |||||||
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Carbamoyl phosphate synthetase I (CPS I) is a
Structure
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. The large subunit contains two active sites, one for the production of carboxyphosphate, and the other for the production of carbamoyl phosphate.[2][3] Within the large subunit there are two domains (B and C) each with an active site of the ATP-grasp family.[1] Connecting the two subunits is a tunnel of sorts, which directs the ammonia from the small subunit to the large subunit.[4]
Mechanism
The overall reaction that occurs in CPSI is:
2ATP + HCO3− + NH4+ → 2ADP + Carbamoyl phosphate + Pi[4]
This reaction can be thought of occurring in three distinct steps.[5]
- Bicarbonate is phosphorylated to form carboxyphosphate
- Ammonia attacks the carboxyphosphate, resulting in carbamate
- Carbamate is phosphorylated to give carbamoyl phosphate
Regulation
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CPSI is regulated by
Metabolism
CPSI plays a vital role in protein and nitrogen metabolism. Once ammonia has been brought into the mitochondria via glutamine or glutamate, it is CPSI's job to add the ammonia to bicarbonate along with a phosphate group to form carbamoyl phosphate.
Related health problems
The main problem related to CPSI is genetics-based. Sometimes the body does
Notes
- PMID 26592762.
References
External links
- GeneReviews/NCBI/NIH/UW entry on Urea Cycle Disorders Overview
- Carbamoyl-Phosphate+Synthase+(Ammonia) at the U.S. National Library of Medicine Medical Subject Headings (MeSH)