urea cycle- metabolism of amino acid

how does ammonium prepare to enter the urea cycle?

carbamoyl phosphate synthetase catalyses reaction of ammonium ion with CO2 to make carbamoyl phosphate.

uses 2ATP

occurs in mitochondrial matrix

how does the ammonium enter the urea cycle now that its prepared?

the carbamoyl group (containing C=O and C=NH3 from ammonium) is taken to the cytosol and transferred onto ornithine from urea cycle

makes citrulline

catalysed by ornithine transcarbamoylase

what happens to citrulline in the urea cycle?

condensed with aspartate to make asparginosuccinate

catalysed by arginosuccinate synthetase using 1 ATP

what happens to arginosuccinate in the urea cycle?

cleaved by arginosuccinase

into arginine (stays in urea cycle) and fumarate (leaves)

what happens to arginine in the urea cycle?

hydrolysed by arginase to make ornithine and urea

urea contains two amine groups: one from the ammonium ion and one from the aspartate that entered. now the ammonium ion is no longer in a toxic form

what happens to ornithine in the urea cycle

reacts with a carbamoyl group from carbamoyl phosphate made in the, mitochondrial matrix to make citrulline. thus, completes the cycle