Purines & Pyrimidines Flashcards
What are the 2 pathways for purine and pyrimidine synthesis?
De novo: uses basic like NH3, CO2, ATP; highly conserved
salvage: recycles borken down nucleic acids
What are purines and pyrimidines?
They are nitrogenous bases that make up the two different nucleotides in DNA and RNA. Purines (adenine and guanine) are two-carbon nitrogen ring bases while pyrimidines (cytosine and thymine) are one-carbon nitrogen ring bases.
Is dietary intake of nucleic acids high?
No, it is pretty minimal. Only about 5% of ingested nucleotides make it into the ciculation. We only absorb about 5%.
De novo purine synthesis begins with ribose-5-phosphate as hte anchor. How is ribose-5-phosphate generated?
Pentose Phosphate Pathway
Ribose-5-phosphate is activated by ATP to form what molecule? What is the enzyme involved?
- PRPP
- the enzyme is PRPP synthetase
- PRPP synthetase is activated by phosphate and inhibitied by purine nucleotides (its end product)
Which enzyme transfers an amino group from glutamine to PRPP to form 5-phospho-ribosylamine?
De novo purine synthesis
PRPP aminotransferase
What is the regulation of the purine de novo pathway?
end-product negative feedback by ADP, AMP, GMP, and IMP
What are the 3 5-star enzymes of the purine salvage pathway?
- adenosine deaminase
- hypoxanthine-guanine phosphoribosyl trasferse (HGPRT)
- xanthine oxidase
In de novo pyrimidine snythesis, carbamoyl phosphate synthetase II converts glutamine and CO2 to carboamoyl phosphate in what part of the cell?
cytoplasm
Where does carbamoyl phosphate synthetase II (CPS II) live?
Where does CPS I live?
CPS II = cytoplasm
CPS I = mitochondria
