Glutamine synthetase adds ammonia to glutamate to form glutamine, which can move into the blood and transport ammonia to the liver.
N-acetylglutamate allosterically activates CPS1, increasing its affinity for ammonia.
Ornithine transcarbamoylase combines ornithine with carbamoyl phosphate to form citrulline in the urea cycle.
In the liver, glutamine is cleaved back into glutamate and ammonia by the enzyme glutaminase, allowing ammonia to enter the urea cycle.
Ammonia is transported to the liver by being converted into glutamine or glutamate, which can then enter the bloodstream.
Aspartate provides the second nitrogen group necessary for the formation of urea in the urea cycle.
Arginine is broken down by arginase to produce urea and ornithine.
Ammonia is the major toxin that results from the metabolism of amino acids.
The final product of the urea cycle is urea, which is less toxic and can be excreted by the kidneys.
The first step involves the enzyme carbamoyl phosphate synthetase 1 (CPS1) converting ammonia, carbon dioxide, and ATP into carbamoyl phosphate.
N-acetylglutamate is crucial for the activation of CPS1, and a deficiency can lead to toxic levels of ammonia.
<p>Aspartate</p>
<p><span style="color: rgb(12, 10, 9)">Fumarate is first converted to malate , and then the enzyme malate dehydrogenase converts malate to oxaloacetate. Oxaloacetate and glutamate are converted to aspartate and alpha-ketoglutarate by the enzyme aspartate transaminase, or AST. This regenerates aspartate, so that it may enter the next urea cycle.</span></p>
ammonia
toxic
argininosuccinate lyase
urea
glutamine, alanine
ornithine transcarbamoylase
second
urea
carbamoyl phosphate synthetase 1 (CPS1)
kidneys
