Urea cycle
Definition The urea cycle (also known as the ornithine cycle) is a cycle of biochemical reactions occurring in many animals that produces urea (NH2)2CO from ammonia (NH3)Function
Organisms that cannot easily and quickly remove ammonia usually have to convert it to some other substance, like urea or uric acid, which are much less toxic. Insufficiency of the urea cycle occurs in some genetic disorders (inborn errors of metabolism), and in liver failure.Urea is less toxic than ammonia. The Urea Cycle occurs mainly in liver. The 2 nitrogen atoms of urea enter the Urea Cycle as NH3 (produced mainly via Glutamate Dehydrogenase) and as the amino N of aspartate. The NH3 and HCO3- (carbonyl C) that will be part of urea are incorporated first into carbamoyl phosphate.
Urea Cycle Enzymes in mitochondria: 1. Ornithine Trans- carbamylase Enzymes in cytosol: 2. Arginino- Succinate Synthase 3. Arginino- succinase 4. Arginase.