L15: Amino Acid & Urea Metabolism Flashcards
(40 cards)
Deamination
What does an amino acid that has been transaminated or deaminated turn into?
Their alpha-keto forms
Happens by replacing amino group with a carbonyl
Deamination
What is the universal acceptor of amino group?
alpha-ketoglutarate, which accepts amino groups/nitrogen in the liver to form glutamate
Deamination
Why must we get rid of the amino group?
Neither TCA nor beta-oxidation processes have a way to deal with them!
- We can only process carbons + hydrogens with these catabolic processes
Deamination
What is the first step in deamination?
Where does this step occur?
Is it reversable?
Transamination
In the liver
Yes, it is reversable
Deamination
What is the mechanism behind transamination?
Reactants
Enzyme
Cofactor - what does it hold?
Products
1) Alpha keto acid accepts amino groups from AA
2) AA becomes alpha-ketoacid
3) Alpha-ketogluterate becomes glutamate
Reactant: Amino Acid + alpha keto acid
Enzyme: Aminotransferases
Cofactor: PLP = temporary amonia holder
Product: Amino acid + alpha keto acid
Deamination
What holds the amonia?
L-glutamine
Deamination
Post transamination, what is the goal?
To get ammonia to the liver
Deamination
What are the two methods though which ammonia is transported to the liver?
Glutamine or Alanine
Deamination
Describe the problem with Glutamate and the liver
Glutamate can be an acceptor molecule in the liver
But can not pass though the membranes whilst carrying ammonia as it is toxic
Deamination
How is glutamine used as a transporter in the liver?
What is the enzymes used during this pathway?
1) Activation of glutamate using ATP
glutamine synthetase
2) Addition of the second equivalent of ammonia to make Gln
glutamine synthetase
Glutaminase chops off ammonia in liver to remake glutamate
glutaminase
Deamination
How is alanine used as a transporter in the liver?
What is the enzymes used during this pathway?
Pyruvate is in high abundance in exercising tissues.
The liver is able to conduct gluconeo, which “packages” pyruvate back into glucose to feed back to the hungry muscles
Net result:
1) Pyruvate + Glutamate -> Alanine
2) Alanine is transferred to the liver
3) In liver Alanine regenerates pyruvate and turns it into glucose
Excretory Forms
What are the 3 Major Excretory Forms of nitrogen?
1) Ammonia
2) Urea
3) Uric Acid
Excretory Forms
What are the traits of Ammonia?
- Alkaline (accumulation raises pH)
- Uses mainly by aquatic animals
Excretory Forms
What are the traits of Urea?
- Neutral
- High water loss when excreted
- Many vertebrates
Excretory Forms
What are the traits of Uric Acid?
- Insoluble
- Excrete w/o lots of water loss
- Birds, reptiles
Ammonia in the liver
How does Ammonia enter the urea cycle?
Via Carbamoyl phosphate
Ammonia in the liver/ Pre-Urea Cycle
How is Carbamoyl Phosphate formed?
What enzyme catalizes the reaction?
1) Activate bicarbonate with ATP
2) Displace phosphate with amino group
3) Activate resulting carbmate with ATP
Enzyme: Carbamoyl Phosphate Synthase 1
Urea Cycle
What are the 4 steps of the urea cycle?
Urea Cycle
Describe the link between the Urea and TCA cycle
The fumarate that leaves the urea cycle become malate
Malate then enters TCA cycle
Urea Cycle Regulation
What are the two key components in Urea Cycle Regulation?
- Arginine increases the production of N-Acetylglutamate
- A lot of arginine = a lot of urea cycle intermediates
- The commitment step, is promoted by N-Acetylglutamate
- N-Acetylglutamate is a signal molecule for a high concentration of both acetyl-CoA (energy) and glutamate (ammonia)
AA Catabolism
What are the 5 cofactors in amino acid catabolism
PLP
Biotin
THF
AdoMet
THB
AA Catabolism
Where is PLP active?
Transamination
AA Catabolism
Where is Biotin active?
One-carbon transfer (CO2)
AA Catabolism
Where is THF active?
One-carbon transfer (intermediate oxidation states)
