Amino Acid Degradation Flashcards
What is the fate of amino acids in the fed and fasting states?
Fed State:
Amino Acids Used for synthetic processes
Fasting State:
Proteins are degraded (in muscle mostly) so Amino Acids can be:
- Used for Energy
- Used for Gluconeogenesis
- Modified to maintain appropriate levels of Amino acids
What insulin counterregulatory hormones are released during fasting?
- Glucagon (Mobilizes Fuels)
- Norepinephrine (stress)
- Epinephrine (stress)
- CORTISOL (long term effect on muscles)
What does Cortisol do?
Provides for changing requirements over the long term - (Tells muscles what to do because Glucagon can’t)
Stimulates:
- Mobilization of Amino Acids from Muscle Protein
- Gluconeogenesis to produce glucose for glycogen synthesis
- Release of Fatty Acids from Adipose
T or F: All 20 amino acids can be broken down into pyruvate, acetyl CoA or a citric acid cycle intermediate.
TRUE, these are used to generate energy, glucose, or storage molecules (Fatty Acids)
What does Cortisol do in the muscle?
- Signals protein breakdown
Categorize the following based on their usage: Alanine Glutamine Leucine Isoleucine Valine
Nitrogen Carriers In Bloode:
Alanine
GLUTAMINE (Major Carrier)
Energy: Branched Chain Amino Acids (BCAAs) Leucine Isoleucine Valine
What explains the fact that the average protein contains very little Alanine and Glutamine, yet they are a large part of Amino Acids in blood?
- While Glutamine and Alanine usually only make up a small portion of any given protein, they are the MAJOR TRANSPORTER OF AMINO ACIDS in the BLOOD.
- Other amino acids like BCAAs are converted to these so they can move through the blood.
What explains the fact that the average amount of BCAAs (leu, Iso, Val) in the blood is substantially less than what is found in a typical protein?
- BCAAs are used as energy (TCA) or are converted to Alanine and Glutamine
- This leaves very little leftover BCAAs to move in the blood
What 3 things can all amino acids be broken down into?
- Pyruvate
- Acetyl-CoA
- Citric Acid Cycle Intermediate
What amino acids are a major fuel source in skeletal muscle and peripheral tissue during fasting?
- BCAAs
What preliminary step must happen before amino acids can be used for energy or stored as fatty acids?
- how is this done?
alpha-amino group (nitrogen) must be removed
2 ways:
- TRANSamination
- DEamination
What is the difference between Transanimation and Deamination?
Transamination:
Moves Amino group between KETO acids
-usually FUNNELS to GLUTAMATE
Deamination:
Removes the ammonia
What is the purpose of transamination reactions?
- To get the right amino acids in the right place (aka FUNNELING AMINO ACIDS)
- To make sure you have appropriate amounts of all amino acids
What are enzymes called that catalyze transamination reactions?
- cofactor
- reversibility of reactions
- Times of high activity
Transaminases
Aminotransferases
PLP (pyridoxal phosphate) coefactor derived from B6 (ALL TRANSAMINATION REACTIONS)
- These reactions are easily reversed
- USED IN BOTH SYNTHESIS OF AA AND DEGRADATION
T or F: all amino acids can undergo transamination reactions.
False, Lysine and Threonine are the only two that can’t
What amino acid is most commonly involved in transamination reactions?
glutamate and alpha-ketoglutarate
What two amino transferases are used as diagnostic markers?
- location
- indications high of markers
ALT (alanine aminotransferase)
- Elevated levels in serum means LIVER damage causing abnormal levels into the bloodstream
- Predominant location = liver
AST (aspartate aminotransferase)
- Elevated levels mean damage to liver or CARDIAC OR SKELETAL MUSCLE.
- Predominant location = liver, cardiac, and sketetal mm.
Where can the transamination products of Isoleucine, Leucine, and valine enter the TCA cycle?
Isoleucine - Acetyl CoA, Succinyl CoA
Leucine - Acetyl CoA
Valine - Succinyl CoA
Succinyl-CoA and Acetyl-CoA from BCAAs is used for what two processes?
- Energy via the TCA cycle
- Glutamine via alpha-ketoglutarate
- some is also used to make alanine
Maple Syrup Urine Disease (MSUD) (aka Branched Chain Ketoaciduria)
- Cause
- Symptoms
- Treatment
- Disorder of alpha-Keto Acid Dehydrogenase complex (autosomal recessive)
- Sweet smelling urine, progressive neurologic damage, seizure etc.
Treament:
- Lifelong restriction of dietary Valine, Leucine, Isoleucine
What enzyme COMPLEX is responsible for turning alpha-Keto acids to Acetyl CoA or Propionyl CoA —> —> Succinyl CoA
alpha-Keto Acid Dehydrogenase
What amino acids become high in the blood with Maple Syrup Urine Disease?
High BCAA in the blood because they can’t be used for energy via their defective alpha-Keto Acid Dehydrogenase Complex
What is generated in the conversion of BCAAs to acetyl CoA or Succinyl CoA?
- NADH and FADH2
* *Note: Acetyl CoA and Succinyl CoA can also be ran through the cycle to get Glutamine
WHAT FIVE AMINO ACIDS CAN YIELD ALANINE WHEN DEGRADED?
- why would such degradation take place
- Cysteine
- Glycine
- Serine
- Threonine (via pyruvate)
- Tryptophan
- This would occur when there is a shortage of alanine or energy
WHAT FOUR AMINO ACIDS CAN YIELD GLUTAMATE?
- reason for this degradation
- Arginine
- Proline
- Histidine (via glutamate)
- Glutamate
- This would occur when there is low energy in the cell or lack of glutamate
What happens to alanine in the fasting state?
- is only alanine degraded?
It is shunted from the muscle into blood then liver for gluconeogenesis
- No alanine is not the only protein degraded BCAAs aminate pyruvate to get Alanine
What amino acids are ketogenic only and cannot make glucose?
- what is ketogenic
- synthetic uses
- Leucine
- Lysine
- Ketogenic means any amino acid that can become Acetyl CoA
- Used for Fatty acid and Ketone Body Synth
What amino acids are glucogenic?
- glucogenic and ketogenic?
The other 18
*Note: all of these can form pyruvate OR a TCA cylcle intermediate
Ketogenic + Glucogenic
- Isoleucine
- Threonine
- All Aromatics (tyr, phe, trp)
T or F: ALL glucogenic can be used in gluconeogenesis
True
What are the three purposes of transporting glutamine to the kidneys?
- TCA cycle - (through alpha-KG)
- Gluconeogeneis - (through alpha-KG)
- Convert Alanine to Serine
Which amino acid in the blood is a major source for gluconeogenesis?
Alanine (transaminated to pyruvate)
Which amino acid is the major carrier for nitrogen in the blood?
Glutamine
T or F: amino acids are also used for energ in the fed state.
True
What happens to those amino acids that are ketogenic during gluconeogenesis?
- Converted to Acetyl-CoA —-> Fatty Acids or Ketone Bodies
Why do BCAAs (Iso, Leu, Val) build up in maple syrup urine disease?
- alpha-ketoacid dehydrogenase doesn’t work
- These amino acids build up because they can’t take the next step to becoming glucogenic and ketogenic intermediates like they usually do
