Urea cycle enzyme

The urea cycle consists of a series of five main enzymes — carbamoyl phosphate synthetase 1 (CPS1), ornithine transcarbamylase (OTC), argininosuccinate synthetase (ASS1), argininosuccinate lyase (ASL), and arginase 1 (ARG1) — working together primarily in the liver to convert highly toxic ammonia, a byproduct of amino acid catabolism, into the much less toxic urea for safe excretion by the kidneys. Additional supporting enzymes and transporters, such as N-acetylglutamate synthase (NAGS) and ornithine/citrulline antiporters, are involved in the cycle’s proper function. Genetic or acquired defects in these enzymes result in urea cycle disorders characterized by hyperammonemia, leading to serious neurological and systemic complications. Several drugs target this pathway by either activating defective enzymes or providing alternative routes for waste nitrogen excretion

Other names

Urea cycle enzymeCarbamoyl phosphate synthetase 1 (CPS1)Ornithine transcarbamylase (OTC)Argininosuccinate synthetase (ASS1)Argininosuccinate lyase (ASL)Arginase 1 (ARG1)

Ammonia scavenging (drugs convert ammonia into excretable conjugates) Activation of N-acetylglutamate synthase (by carglumic acid)