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Amino Acid Metabolism 2

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What does ALT and AST in serum mean?
It means that tissue lysis has occured because aminotransferases are intracellular. Indicator for hepatitis, heart or muscle damage.

ALT = alanine AT Ala -> Pyr
AST = asparate AT Asp -> OAA
What enzyme comes from Vit B6?
Pyridoxal Phosphate (PLP)

*Which aminotransferaces need as a cofactor
*If absent in enfant formula,causes convulsions b/c neurotransmitters not maed.
What are the forms of Nitrogen that enter the Urea Cycle? What do they form?
*NH4+ forms carbomyl phosphate in the mitochondria using CPSI, 2 ATP and CO2

*Aspartate ultimately leaves as fumarate, and nitrogen says in arginine
(cytoplasm)
5 Steps of Urea Cycle
1. activation of NH4+, reacts w/CO2, 2 ATP using carbamoyl phosphate synthetase I (CPSI) to form CARBAMOYL PHOSPHATE
2. carbamoyl phosphate reacts w/ORNITHINE to make CITRULLINE with enzyme ORNITHINE TRANSCARBOXYLASE (mitochondria)
3.-5. add ASPARATE to CITRULLINE in cytoplasm
-4 C of aspartate taken off as fumarate and N used to make ARGININE
-cleave off amidino of Arginine to make UREA and regenerate ORNITHINE
Why does urea production increase during fasting?
During fasting, your body runs out of glycogen and needs to keep the blood glucose level up. So the body breaks down intracellular proteins to scavenge for aa to make glucose. The carbon skeletons are feed into gluconeogenesis and the nitrogen is excreted as urea. As the body adapts to fasting, tissues shift from glucose usage to ketone bodies.
How can we control the flow of nitrogen in to the urea cycle?
*transcriptional repression
*control at CPS I level
-required allosteric effector NAG, that positively affects CPS I
-NAG is made from glutamate and acetyl CoA, whose reaction if positively controlled by ARGININE
*TEST*
What are the activators of the Urea Cycle?
*Arginine
*NAG
*Glutamate
*Ammonia - substrate availability
What happens during liver failure?
What can be done?
*No urea made
*Ammonia builds up
*Toxicity occurs
*Coma, death

*Activate urea cycle
*Transplant
what happens during kidney failure?
What can be done?
*Urea builds up
*Later ammonia builds up
*Death

*Dialysis
*Low protein diet
In hereditary disorders, how is nitrogen excreted?
*Serine -> Glycine -> Hippurate (that is excretable)

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