LECTURE 29 - UREA CYCLE Flashcards
which groups serve as co factors for transaminases?
PLP
PMP
Vit B6
which enzymes prefer alpha KG as a substrate?
glutamate dehydrogenase
aspartate transaminase
tyrosine aminotransferase
who discovered the urea cycle
first metabolic pathway defined
discovered by hans adolf krebs and hanseleit
hans krebs did the CAC
what are the sources of NH4+ in the urea cycle?
comes from glutamine (glutaminase) and glutamate (glutamate dehydrogenase)
in which cell compartments does urea cycle happen?
mitochondria and cytoplasm
what is the rate limiting of the urea cycle?
carbamoyl phosphate synthetase 1 (CPS1)
makes carbamoyl phosphate
CPS1 uses 2ATP and HCO3- which comes from CAC (which is also in the mitochondria!)
carbamoyl phosphate is the first substrate of the urea cycle
happens when high ATP concentration
what is the CPS1 reaction?
creates a high energy intermediate
how is CPS1 regulated?
allosterically activated by N-acetylglutamate (NAG)
NAG is produced by NAG synthase (NAGS)
NAGS is stimulated by arginine
NAG production is proportional to concentration of arginine
more arginine = more urea cycle, activates CPS1
synthesis of NAG
CPS2 vs CPS1
what are the different ways humans can have hyperammonia
what is the first step of the urea cycle?
ornithine and citrulline use the same transporter
what is step 2 of the urea cycle?
what are steps 3 and 4 of the urea cycle?
where do the nitrogens come from?
aspartate transaminase, which makes aspartate from oxaloacetate is found in mitochondria of liver
the oxaloacetate comes from the CAC, and the fumarate will join back into the CAC
graphic that explains link between urea cycle and CAC
what is the energy cost and energy gain of the urea cycle?
