Ch. 22 Amino Acid and Nucleotide Synthesis Flashcards
What are amino acids broken down to?
Amino acids are broken down to urea and excreted.
How is the nitrogen from amino acids transported? (2)
Nitrogen from amino acids is ALWAYS transported as glutamate and glutamine.
What do you need for amino acid synthesis?
You need a nitrogen/ammonia source.
What is the nitrogenase complex? Write out the reaction.
It catalyzes the nitrogen assimilation reaction…
N₂ + 10 H⁺ + 8 e- + 16 ATP→2 NH₄ + 16 ADP + 16 Pᵢ + H₂
Where is the nitrogenase complex found? (kind of 2)
It only exists in a small population of bacteria and archaea. Legume symbiosis with bacteria is a common place to find this.
Why do bacteria undergo symbiotic relationships with plants as it relates to amino acid synthesis?
It takes a lot of ATP to make ammonia/nitrogen so bacteria use the plant’s excess ATP.
How does the nitrogenase complex work?
ATP causes a conformation change in the complex, driving the reaction forward.
What happens to the nitrogen/ammonia fixed in the nitrogenase complex?
The nitrogen fixed into ammonia in these bacteria are incorporated to glutamate and glutamine.
ALL plants and animals circulate glutamate and glutamine as a source of nitrogen/ammonia.
What is glutamine synthetase?
An enzyme that catalyzes the two-step conversion of glutamate to glutamine with ATP.
(look at notes for reaction diagram pg. 61)
Where is glutamine synthetase found?
Found in ALL organisms.
How can glutamine be converted to glutamate? Which direction does it go?
glutamine + ɑ-ketogluterate (CA cycle) → 2 glutamate
This is a constant interconversion based on the organisms needs.
What is glutamate dehydrogenase?
An enzyme that catalyzes the reaction of ɑ-ketogluterate and ammonia to glutamate.
Where is glutamate dehydrogenase found?
It is found in animals.
Where does the ammonia for the glutamate dehydrogenase reaction come from? (2)
Ammonia for this reaction comes from amino acid or nucleic acid catabolism. It is coupled/linked.
What is glutamine synthetase in regards to regulation?
It is the main regulatory enzyme of amino acids anabolism with 12 subunits.
What inhibits glutamine synthetase? (3)
- AMP allosterically inhibits
- CTP allosterically inhibits
- post-translational modification
Why is it cool that the AMP and CTP allosterically inhibit glutamine synthetase?
Each inhibitor can bind individually and it takes two or more to inhibit the enzyme.
How do post-translational modifications inhibit glutamine synthetase?
Adenylation from ATP via adenyl transferase inactivates the enzyme. Adenylated=inactive.
What is adenyl transferase?
An enzyme that either transfers/covalently attaches adenosine to glutamine synthetase (inactive), or it clips the adenosine off (acitve).
What are the three pathways that precursors for amino acid synthesis come from?
Glycolysis, Citric Acid Cycle, and the Pentose Phosphate Pathway. (where carbon comes from, nitrogen comes from glutamate or glutamine)
How are amino acids grouped for synthesis?
Amino acids are grouped into families based on precursors.
What are the families of amino acid precursors? (6)
ɑ ketogluterate (C: CA cycle)
3-phosphoglycerate (C: glycolysis or FA metabolism)
oxaloacetate (C: CA cycle or pyruvate)
pyruvate (C: glycolysis)
phosphoenolpyruvate
ribose-5-phosphate
What amino acids are in the ɑ ketogluterate family? (4)
glutamate
glutamine
proline
arginine
What amino acids are in the 3-phosphoglycerate family? (3)
serine
cysteine
glycine
