General
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Carbamoyl-phosphate synthetase 1 (CPS1) is a mitochondrial enzyme encoded by the CPS1 gene in humans. It catalyzes the first and rate-limiting step of the urea cycle, converting ammonia and bicarbonate into carbamoyl phosphate. This reaction is crucial for detoxifying excess nitrogen by converting ammonia into urea, which is then excreted by the kidneys (Pierson and Brien, 1980; Rubio and Grisolia, 1981; Pekkala et al, 2009; Diez-Fernandez et al, 2013; reviewed in Martinez et al, 2010; Nitzahn and Lipshutz, 2020). CPS1 is predominantly expressed in the liver and plays a vital role in nitrogen metabolism. It is also present in the enterocytes of the small intestine, where it contributes to pyrimidine biosynthesis and the production of circulating citrulline and arginine (Ryall et al, 1985). CPS1 activity is regulated by various factors, including the availability of its allosteric activator, N-acetyl-L-glutamate (NAG), and hormonal signals such as glucagon and glucocorticoids (Rubio et al, 1983; Pekkala et al, 2009; de Cima et al, 2015).
