amino acid plus alphaketoglutarate

form a compound that contains R group and glutamate

example: alanine -> pyruvate

gluamate becomes a Schiff base (double bond NH2)

schiff base releases NH4+ and alphaketoglutarate

in the mitochondral matrix

uses NAD or NADP

only produced in mammals, amphibians, few fish

others make uric acid (birds and reptiles) or ammonia (fish)

1 Nitrogen from Ammonium

1 nitrogen from aspartate

first step

uses ATP to combine NH3 and HCO3- into carbamoyl phosphate

anhydride bond in carbamoyl phosphate is transferres to ornithine to form citrulline

citrulline is transferred to the cytosol

citrulline is combined with aspartate

condensation rxn

ATP is used; AMP and PPi are released

mitochondria: citrulline is pumped out by antiporter and ornithine is pumped in

link to gluconeogenesis

breaks down arginosuccinate into argininine and fumarate

fumarate is used for other processes including recreating aspartate to continue cycle

breaks down arginine into ornithine and urea

uses H2O

ornithine goes back to mitochondria for CAC

Urea is created in the liver so it is excreted later

rctnts: CO2 + NH4 + 3ATP + Aspartate + 2H2O

prod: urea + 2ADP + Pi + AMP + PPi + fumarate

phenylalanine hydroxylase is absent or deficient

used to convert phenylalanine to tyrosine

normally 2/3 of F is converted to Y and 1/3 is made to other proteins

phenylalanine builds up in tissues causing mental retardation

mechanism unknown

can be controlled with diet

destabilizing: arginine, leucine

stabilizing: methionine, proline