7.5: Ciclo de Urea
- Page ID
- 53687
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El ciclo elimina el amoníaco libre (como ión amonio) que es tóxico si se acumula. La reacción de captura también requiere ATP y bicarbonato, y el producto es fosfato de carbamoil. Esta molécula se combina con el aminoácido no proteico conocido como ornitina para producir otro aminoácido no proteico conocido como citrulina. La adición de aspartato a citrulina crea argninosuccinato, que separa un fumarato, creando arginina (una fuente de arginina). Si no se necesita arginina, se puede hidrolizar para producir urea (excretada) y
ornitina, completando así el ciclo.
Las dos primeras reacciones aquí descritas ocurren en la mitocondria y las restantes ocurren en el citoplasma. Las moléculas del ciclo de la urea que intersectan otras vías incluyen fumarato (ciclo del ácido cítrico), aspartato (metabolismo de aminoácidos), arginina (metabolismo de aminoácidos) y amoníaco (metabolismo de aminoácidos).