Home > Urea cycle
The Urea Cycle is a cycle of biochemical reactions occurring in many animal organisms that produces urea from ammonia. This cycle, also known as ornithine cycle, was the first metabolic cycle discovered (Krebs and Hensenleit, 1932)Urea is much less toxic than ammonia, therefore organisms which can't easily and quickly remove ammonia usually have to convert it to some other substance, like urea or uric acid. Insufficiency of the urea cycle occurs in some genetic disorders ( inborn errors of metabolism), and in liver failure . The result in liver failure is accumulation of nitrogenous waste, mainly ammonia, which leads to hepatic encephalopathy.
Reactions of cycle:
- NH3 + CO2 + 2 ATP → carbamoyl phosphate + 2 ADP + Pi ( catalyzed by carbamoyl phosphate synthetase )
- carbomyl phosphate + ornithine → citrulline + Pi
- citrulline + aspartateAspartic acid or aspartate is one of the 20 most common natural amino acids which are the building blocks of proteins. As its name indicates, it is the acidic analog of asparagine, with a carboxylic acid component to its side chain. It is non-essential in + ATP → argininosuccinate + AMPThe three-letter abbreviation AMP can refer to the following: In biology, the nucleotide adenosine monophosphate As a flavour enhancer, the nucleotide adenosine monophosphate In computing, an audio decoding engine made by Tomislav Uzelac and others, which + PPiIn chemistry, pyrophosphate or PP is an anion observed in living systems, usually formed by the hydrolysis of ATP into AMP. The hydrolysis is called pyrophosphorolysis''. ATP → AMP + PP The pyrophosphate anion has the structure PO4-, and is an acid a ( catalyzed by argininosuccinate synthetase)
- AMP + ATP → 2 ADP
- PPi + H2O → 2 Pi
- argininosuccinate → arginineArginine is one of the 20 most common natural amino acids. Is has guanidino side chain functional group. In non-hepatic tissues, arginine can be biosynthesized by the ornithine cycle (or urea cycle). Even so, arginine is often classed as one of the 10 ess + fumarateFumaric acid also called allomaleic acid 2- butenedioic acid boletic acid or lichenic acid is a colorless crystalline flammable carboxylic acid with a fruitlike taste and chemical formula . Irritating maleic anhydride fumes are produced by its combustion. ( catalyzed by argininosuccinase)
- arginine + H2O → ornithine + urea ( catalyzed by arginase)
- ornithine + NH3 + CO2 → citrulline + H2O ( catalyzed by ornithine transcarbamoylase)
Summary reaction:
Biochemistry
