Week 10 - Protein Metabolism (ELE content only) Flashcards
What part of the aa will provide us with energy?
Carboxylic group
Small % tho
What happens in transamination reactions?
Amino group from 1 aa is transferred to glutamate.
What enzyme carries out transamination
Aminotransferase
What happens to the remaining carbon skeleton in a transamination reaction?
Becomes an alpha keto acid
useful for the TCA cycle
Can transamination reactions be reversible for essential aa? WHY?
No
Can’t synthesise their carbon skeletons.
Give examples of aa-specific aminotransferases
Alanine aminotransferase (important in liver due to producing pyruvate as the a- keto acid)
Aspartate aminotransferase (prod oxaloacetate = compound in TCA cycle)
What can an increase in the circulating level of Alanine aminotransferase and Aspartate aminotransferase indicate?
That the body has ⬆️ the use of aa for energy (not normal).
This ⬆️ in aa degradation might indicate trauma or liver disease
What is the difference between the deamination + transamination reaction?
Removal + elimination of end group in deamination reaction. – NH4+
– Taking place mostly in liver but can also happen in muscle when exercising at high intensity
EQUATION for step 1 of the urea cycle
NH4+ + HCO-3 + 2ATP – (carbamoyl P synthetase) –> Carbamoyl P + 2ADP + Pi
Which part of the urea cycle step 1 continues in the urea cycle for further processing?
Carbamoyl phosphate
Step 2 of the urea cycle
Carbamoyl P enters Urea cycle by combining w/ ornithine to prod. citrulline.
Urea cycle:
Citrulline –> Argininosuccinate –> Arginine + fumerate (fumarate leaves cycle) –> Ornithine
What aids the conversion reaction of citrulline –> argininosuccinate in the Urea/Ornithine cycle
Citrulline – ( Aspartate + ATP enter )(Aginiosuccinate synthetase) –> Argininosuccinate + AMP + PPi
What aids the conversion reaction of argininosuccinate to arginine + fumarate in the Urea/Ornithine cycle
Argininiosuccinate lyase
Argininosuccinate – ( argininiosuccinate lyase) –> Arginine + fumarate
What aids the conversion reaction of arginine to ornithine in the Urea/Ornithine cycle
Arginine – (H20 + arginase) –> urea + ornithine
Urea leaves cycle
Why is the urea/ornithine cycle considered costly
Uses 4 ATP
- 2 in step 1
- 2: ATP –> AMP (instead of ADP)
Elimination forms of excess nitrogen between aquatic animals, mammals + reptiles
Aquatic = Ammonia
Mammals = Urea
Many reptiles = Uric acid
What is glutamine essential for?
Lymphocyte proliferation
Cytokin production
Macrophage phagocytosis
What is the availability of glutamine compromised by in catabolic situations?
By the impaired balance between the release/uptake from bloodstream + key organs (gut, liver + skeletal muscle)
List the BCAAs
Leucine
Isoleucine
Valine
(Essential aa)
What can leucine stimulate
Protein synthesis - translation
Where are the BCAAs mostly metabolised
In skeletal muscle
Less in liver
Is the initial transamination of BCAAs reversible?
NO
Due to being essential aa
What do ALL BCAAs produce?
Glutamate
What can the glutamate produced from BCAAs be used for?
To produce alanine + a-ketoglutarate
What does ACDH stand for
Acyl CoA dehydrogenase
What are the enzymes for the steps of catabolising BCAAs
BCAAs share same enzymes for each of the 3 steps
- BCAAT (Branched chain aa aminotransferase)
- BCKAD (Branched chain keto acid dehydrogenase)
- ACDH (Acyl CoA dehydrogenase)
What are the options of end products from the breakdown of the BCAAs
Can either be:
- Ketone body that can’t be converted into glucose
- Compound that can be converted into glucose
aa metabolism during moderate intensity exercise
Mostly BCAAs used as energy (due to being an ⬆️ in the release of alanine from muscle telling us there’s protein breakdown).
Carbon skeletons of these then provide as intermediates of the TCA cycle.
Also an ⬆️ in glutamate uptake from blood which depends on glycogen storage levels (starts at low or depleted glycogen)
aa metabolism during high intensity exercise
Less glutamine prod to favour a-ketoglutarate.
As contraction ⬆️ = prod of AMP + H+ ⬆️
– leads to activation of adenylate deaminase which ⬆️ prod or conc of IMP + NH3
What does IMP mean
Inosine monophosphate
What is the particular metabolism happening at high intensity exercise?
Purine metabolism
What is often used as a fatigue marker in muscles?
NH3
