Nucleic Acid Metabolism Flashcards
What are the two pathways to make necleotides?
De novo and salvage pathways
What is the beginning of nucleotides in de novo synthesis pathways?
Synthesis of ribonucleotides
Why would blocking de novo have little effect?
If cell has source of bases or nucleotides, salvage pathway can be used
Why would blocking the salvage pathway have little effect?
Cells could synthesize nucleotides by the de novo pathway
Where does de novo synthesis occur?
Cytosol
Where is the purine ring synthesized in de novo?
1’ carbon of ribose 5-phosphate
What is the first nucleotide formed in de novo purine synthesis?
Inosine monophosphate (IMP)
What are the steps of IMP synthesis?
- Activation of ribose-5-phosphate?
- Acquisition of purine atom N9
- Purine ring completion by successive activation of carbon-bound oxygen by phosphorylation
What stimulates or inhibits AMP synthesis?
Low GTP INHIBITS
Hight GTP STIMULATES
How is de novo purine synthesis inhibited?
High IMP, AMP, GMP
How is de novo purine synthesis stimulated?
High PRPP
True or false. De Novo synthesis of pyrimidine nucleotides is non-linear.
False; it is linear.
What are the steps of de novo synthesis of pyrimidine nucleotides?
- Synthesis of UMP
- Synthesis of carbamoyl aspartate
- Ring closure to form dihydroorotate
- Oxidation of dihydroorotate
- Acquisition of ribose phosphate
- Decarboxylation of OMP to form UMP
What do nucleotide kinases do?
Convert monophosphates to di- and tri-phosphates
What are the three types of salvage enzymes?
Nucleoside kinases
Nucleoside phosphorylases
Phosphoribosyl transferases
