L21: AA Catabolism & Nitrogen Disposal (may) Flashcards
Why is removing the α-amino group so important?
- Because that’s the first step in most AA degradation pathway
* (or you can just say it’s the first step in aa catabolism)* - Because it is essential for energy production from AA carbon skeleton
What is the fate of the AA nitrogen?
- It’s incorporated into other compounds
- Excess AA will be excreted as urea
What are the 3 steps that produce urea?
- Transamination
- Oxidative Deamination
- Urea cycle
She9eer ib transamination blthab6?
It’s the first step in catabolism where il AA transfers its α-amino group wiya il α-ketoglutarate; this forms α-keto acid and glutamate.
Il transfer elly y9eer ib transamination is catalyzed by what?
Transaminases (Aminotransferases)
Where can transaminases be found?
in the mitichondria and cytosol
What are the 4 characteristics of Transaminases?
- Substrate specificity
- Mechanism of action
- Reaction equilibrium
- Diagnostic value
Alanine Aminotransferase (ALT) is in involved bas ib reactions involving Alanine & Aspartate Aminotransferase (AST) nafs il shay with Aspartate.
This is an example of what?
Substrate specifity in transamination
All transamination reactions require?
the coenzyme pyridoxal phosphate (PLP)
PLP (pyridoxal phosphate) is a derivative of?
Vitamin B6
What is the equilibrium constant in transamination reactions? and why? and shnu faydat hal shay?
The equilibrium constant is near 1 because the reaction is bi directional, thus, have a role in both AA degradation AND synthesis pathways.
what are indicators/diagnostic markers of most liver diseases, myocardial infarction, and muscle disorders?
High ALT & AST
Where does oxidative deamination take place?
liver and kidney
The liver and the kidneys have a specific dehydrogenase that carries out oxidative deamination of AA’s named what?
glutamate dehydrogenase
Shesawee glutamate dehydrogenase blthab6?
it liberates the amine group as a free ammonia (NH3)
What is the only AA that undergoes rapid oxidative deamination?
glutamate
Shnu products il oxidative deamination? w laish nabeehum?
- α-ketoglutarate: enters the central pathway of energy metabolism
- Ammonia: source of Nitrogen for urea synthesis
What is urea?
The major disposal form of amino groups derived from AAs
or just the end product of protein metabolism
Urea accounts for?
about 90% of the nitrogen-containing components of urine
What are the origins of urea molecules?
- One nitrogen from free ammonia
- The other nitrogen from aspartate
- The carbon and oxygen are derived from CO2
Urea is produced by? Then transported to?
Produced by: the liver
Transported to: the kidneys for urinary excretion
Describe the urea cycle
What is the rate limiting step in the urea cycle?
Carbamoyl phosphate synthetase I
What is an indicator of high levels of nitrogen in your body?
Arginine
What will activate OR shut down the urea cycle?
Activate the urea cycle: HIGH levels of Nitrogen
Shut down the urea cycle: LOW levels of nitrogen
What is an activator of N-Acetylglutamate (NAG) synthesis?
Arginine
N-Acetylglutamate (NAG) is an essential what?
allosteric activator for carbomyl phosphate synthetase 1
(allosteric activator ya3ni it binds to an enzyme at a site other than the active site to enhance its activity)
high levels of arginine enhances reaction shnu w shnu 3shan ya36eena NAG?
enhances il reaction between Glutamate & Acetyl CoA
Describe she9eer laman you ingest a protein rich meal?
Ingestion of a protein-rich meal → ⬆️ [glutamate] (substrate & regulator of NAG synthesis) → ⬆️ [NAG] → ⬆️ CPSI activity → ⬆️ rate of urea synthesis.
