Search results
Results from the WOW.Com Content Network
The urea cycle converts highly toxic ammonia to urea for excretion. [1] This cycle was the first metabolic cycle to be discovered by Hans Krebs and Kurt Henseleit in 1932, [2] [3] [4] five years before the discovery of the TCA cycle. The urea cycle was described in more detail later on by Ratner and Cohen.
The excretion of urea is called ureotelism. Land animals, mainly amphibians and mammals, convert ammonia into urea, a process which occurs in the liver and kidney. These animals are called ureotelic. [3] Urea is a less toxic compound than ammonia; two nitrogen atoms are eliminated through it and less water is needed for its excretion.
Mutations in the human ASL gene causes argininosuccinic aciduria, a rare autosomal recessive disorder, and results in deficiencies of the urea cycle. Argininosuccinate lyase is an intermediate enzyme in the urea synthesis pathway and its function is imperative to the continuation of the cycle.
Main page; Contents; Current events; Random article; About Wikipedia; Contact us; Donate
The transformation of citrulline into argininosuccinate is the rate-limiting step in arginine synthesis. The activity of argininosuccinate synthetase in arginine synthesis occurs largely in at the outer mitochondrial membrane of periportal liver cells as part of the urea cycle, with some activity occurring in cortical kidney cells.
In animals, the main excretory products are carbon dioxide, ammonia (in ammoniotelics), urea (in ureotelics), uric acid (in uricotelics), guanine (in Arachnida), and creatine. The liver and kidneys clear many substances from the blood (for example, in renal excretion), and the cleared substances are then excreted from the body in the urine and ...
In land-dwelling animals, it is an intermediary metabolite in nitrogen disposal through the urea cycle and the synthesis of pyrimidines. Its enzymatic counterpart, carbamoyl phosphate synthetase I (CPS I), interacts with a class of molecules called sirtuins , NAD dependent protein deacetylases, and ATP to form carbamoyl phosphate.
It represents the first committed step in pyrimidine and arginine biosynthesis in prokaryotes and eukaryotes, and in the urea cycle in most terrestrial vertebrates. [2] Most prokaryotes carry one form of CPSase that participates in both arginine and pyrimidine biosynthesis, however certain bacteria can have separate forms.