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1. What are the indispensable AAs? (9)
2. Conditionally dispensable? (2)
3. Special? (3)
1. Isoleucine, leucine, valine, lysine, methionine, threonine, tryptophan, phenylalanine, histidine
2. Cysteine & tyrosine
3. Citrulline, ornithine, homocysteine
1. What are sources of C and N for synthesis of dispensible AAs (DAAs?)
2. What is central to AA transamination? (2)
3. What vitamin is required?
4. What direction does transamination proceed in?
5. where are transaminases present? 5
1. A-ketoglutarate --> glutamate (central role). Cs come from TCA/glucose metabolism.
Glutamate supplies most of C and N to AAs.
2. Gluatamate and a-ketoglutarate + NH3
3. B6 (pyridoxal phosphate)
4. Both directions rapidly
5. Most tissues (liver gut kidney muscle brain)
1. What can glutamate turn into? (6)
2. What is central role of glutamate in AA metabolism?
3. When does kidney extract significant glutamine?
4. What does muscle release most of its AAs as? % (2)
5. What is generally major organ extracting glutamine? What else can it do?
6. What is the glucose-alanine shuttle?
7. What do all of these processes cost?
1. Leucine, isoleucine, valine, alanine, arginine (and a-ketoglutarate), glutamine
2. Ammonia regulation, transamination, glutamine syn/degradation.
3. When its dumping acid
4. ~50% alanine and glutamine
5. Gut. Oxidize glutamine --> NH3
6. Way to shuttle N generated from AA oxidation out of muscle and to liver for urea synthesis.
1. Where does N in urea come from?
2. What is the main enzyme for urea synthesis?
3. Where does urea synthesis occur?
4. Describe net flow of N in normal metabolism
5. What happens if there's a blocked flow?
6. How does protein intake affect urea?
- 1. Glutamate/glutamine
- 2. Carbamoyl phosphate, requires 3 ATP total for urea synthesis
- 3. Mitochondria
- 4. Muscle (gln/ala) --> liver --> becomes glutamate --> urea cycle.
5. High NH3 concentration --> will die.
6. Urea excretion reflects protein intake.
1. What do gut bacteria do with urea?
2. Can liver arginine exchange with EC arginine?
3. What are important compounds from serine? 3
4. What is cycle of sulfur AA metabolism? (4)
5. What is needed for homocysteine --> methionine?
6. What is needed for homocysteine methyltransferase? (homocysteine --> methionine)
1. Hydrolyze urea to NH3 and CO2 (H. Pylori) NH3 goes back to liver.
3. Choline, glycine betaine, ethanolamine. METHYL GRUOPS COME FROM SAM!!!!!!'
4. SAM --> S-adenylhomocysteine --> homocysteine --(remethylation)-> methionine --(transmethylation) --> SAM.
5. For primary remethylation pathway of methionine, requires vitamin B12 (also seen in glucose metabolism)
6. B12, B9, B6 --> methyl THF is dependent on these 3 vitamins.
1. What does cysteine availability depend on?
2. What is glutathione? What AAs does it contain? (2)
3. How does phenylalanine degradation occur? Through what enzyme? What happens if you don't have this enzyme?
4. What is the most common AA inborn error?
5. Treatment? (2)
6. What is the source of catecholamines?
1. Methionine levels.
2. Major antioxidant - scavenges reactive oxygen species by forming disulfide bonds (cysteine, glycine!!!)
3. Through tyrosine. PHenylalanine hydroxylase. PKU
5. Low phenylalanine levels with Tyr supplementation
6. Tyrosine --> LDopa --> Dopamine --> Ep/NE
1. What happens if you have defect in BKAA DH?
1. BKAA is important for breaking down BCAA (isoleucine, leucine, valine). Without it --> maple syrup urine disease.