Nitrogen Metabolism/urea cycle

What happens with aspartate transaminase?

Take amine from aspartate, give to alpha-keto glutarate, and get glutamate. Also left with oxaloacetate (which is important for gluconeogenesis)

describe the rxn AST (or SGOT) does. What does the TCA cycle have to do with it?

Takes aspartate+alpha-ketoglutarate and makes oxaloacetate and glutamate (and vice versa). Oxaloacetate and alpha-ketoglutarate are in the TCA cycle so it's easy to move an AA into or out of the TCA cycle using this rxn

Does N-acetyl glutamate inhibit or activate carbamoyl phosphate synthetase?

activates it. So as glutamate levels increase convert some of this to stimulate the urea cycle to get rid of it

Why would a patient with Urea cycle defect need have mental and CNS problems?

ammonia crosses the BBB and can destroy brain cells

*What are the direct donors of nitrogen in the urea cycle?

aspartate and carbamoyl phosphate

*Hyperammonemia II is an enzyme deficiency in ____. What would you see in that patient?

carbamoyl phosphate synthetase Low BUN, nitrogen levels going up, glutaminase levels go up

*Name the two urea cycle enzymes we're supposed to remember

carbamyl phosphate synthetase ornithine transcarbamylase

Deficiency in ____ and ____ cause hyperammonemia

carbamyl phosphate synthetase ornithine transcarbamylase both found in mitochondrial matrix

Citroline ___ the mitochondria while ornithine ____ the mitochondria

citroline leaves the mitochondria while ornithine enters the mitochondria

for the urea cycle, where is the arginine?

cytosol

What does glutaminase do?

generate ammonium ion in the kidney (takes glutamine to glutamate in the process). Glutamine synethetase is the opposite (takes glutamate to glutamine

what happens with transamination?

get aspartate

What happens with deamination?

get free nitrogen

Treatment options for someone with Urea cycle defect

give alpha-ketoglutarate (bc turns into glutamate when nitrogen put on it, so alpha-ketoglutarate is needed to sequester the nitrogen

_____ can be intra or extracellular carrier of nitrogen

glutaminase???????

* Where do you find L-amino acid oxidase and D-amino acid oxidase and why is that important?

in the peroxisomes because we sequester peroxide there and detoxify it.. and do the same thing with ammonia (this is compartmentalization to help protect us)

Why is glutamate dehydrogenase (GDH) so important?

it makes ammonia (from glutamate) which is the nitrogen necessary for urea.

What is the point of the Cahill (glucose-alanine) cycle?

it's a protective mechanism to conserve glucose carbons/backbone

*Hyperammonemia I is an enzyme deficiency in ____. What would you see in that patient?

ornithine trancarbamoylase. BUN goes down, carbamoyl phosphate increases (gets into the cytosol where it normally isn't and it can be used there for pyrimidine biosynth), elevated orotic/uracil acid

What is the alpha-keto acid of alanine?

pyruvate. Tranfer amine group off alanine and get pyruvate

Citroline and ornithine are involved in what cycle?

urea cycle

What is a vitamin that's required for the transamination reactions?

vitamin B6.... something to do with PLP (pyridoxal phosphate). PLP (with vitamin B6 requirement) is a docking station to transfer the amine from one amino acid to form another amino acid.

ALT (alanine aminotransaminase) is the same thing as ____. What does this do in a reaction?

(SGPT) glutamate-pyruvate transaminase. An amine is taken from glutamate and given to pyruvate to form alanine and left with alpha-ketoglutarate

What is the extracellular carrier of nitrogen?

Alanine So glutamate is intracellular carrier of nitrogen while alanine is the extracellular carrier of nitrogen.

what are the nitrogen sources for urea?

Ammonia and aspartate

*What is the intracellular carrier of nitrogen?

Glutamate

AST (aspartate amino transaminase) is the same thing as _____

SGOT (serum glutamate oxaloacetatetransaminase)