Salvage pathway of purine nucleotide synthesis are used by all EXCEPT:
Salvage pathway occurs in: Brain RBCs WBCs Bone marrow. Brain, RBCs, WBCs and bone marrow lack the enzyme PRPP Glutamyl Amidotransferase and depends on the exogenous purine nucleosides to form nucleotides. Liver is the major site for denovo purine nucleotide synthesis 5 ATPmolecules are required for de novo purine synthesis. Summary of steps of purine synthesis: Step Donor Added atom Product 1.- Activation of R-5-P (ATP required) PRPP 2.Glutamine N9 (Rate limiting) PRA 3.Glycine (ATP required) C4,5,N7 GAR 4.Methenyl-THFA C8 FGAR 5.Glutamine N3 (ATP required) FGAM 6.- Ring closure (ATP required) AIR 7.Carbon dioxide C6 ACAIR 8.Aspaic acid N1(ATP required) SAICAR 9.- Fumarate removed AICAR 10.Formyl-THFA C2 FAICAR 11.- Ring closure
Leukocytes
Liver
RBC
Brain
Nucleotides