Carbamoyl-phosphate synthase [ammonia], mitochondrial (CPS1) (CPS1)

Carbamoyl-phosphate synthase [ammonia], mitochondrial (CPS1) is a critical ligase enzyme located within the mitochondrial matrix of hepatocytes and intestinal enterocytes [1, 6]. It serves as the rate-limiting step of the urea cycle, where it catalyzes the condensation of ammonia, bicarbonate, and two molecules of ATP to produce carbamoyl phosphate [7, 12]. This reaction is fundamental for the detoxification of neurotoxic ammonia, a byproduct of protein catabolism, into urea for safe excretion by the kidneys [6, 12]. The enzyme is unique in its absolute requirement for N-acetyl-L-glutamate (NAG) as an obligate allosteric activator, which regulates the flux of nitrogen through the cycle [11, 13]. Genetic mutations in the CPS1 gene result in carbamoyl phosphate synthetase 1 deficiency, a rare autosomal recessive disorder that causes severe neonatal or late-onset hyperammonemia [5, 12]. Without functional CPS1, ammonia accumulates rapidly in the blood, crossing the blood-brain barrier and leading to lethal cerebral edema or irreversible neurological damage [12]. In the clinical setting, carglumic acid is utilized as a therapeutic agent that mimics NAG, effectively activating CPS1 to treat hyperammonemia in specific metabolic disorders [14]. Recent research has also highlighted the role of CPS1 in oncology, where its overexpression in certain tumors supports the de novo pyrimidine biosynthesis needed for rapid cell proliferation [9, 10]. Consequently, CPS1 has emerged as a promising target for cancer therapy, with experimental inhibitors like H3B-120 being developed to disrupt ammonia metabolism in malignant cells [10].

Other names

Carbamoyl-phosphate synthetase 1CPSase ICPSICarbamoyl-phosphate synthase 1CPS1

Drugs targeting this enzyme typically act as positive allosteric modulators (such as carglumic acid) to restore catalytic function by mimicking natural activators in deficiency states, or as allosteric inhibitors (such as investigational H3B-120) to block ATP hydrolysis and disrupt nitrogen flux in overexpressing cancer cells.