Class 5: Nucleotide Metabolism Flashcards
nucleoside
nitrogen base + sugar
nucleotide
nitrogen base + sugar + phosphate
3 components of nucleotide
1) nitrogen containing base: purine or pyrimidine
2) pentose (sugar)
3) phosphate groups
Name the purines
adenine
guanine
name the pyrimidines
cytosine
thymine
uracil
difference between DNA and RNA nucleotides
Base: Thymine for DNA, Uracil for RNA
Sugar: Deoxyribose for DNA, ribose for RNA
De novo pathways
base itself is synthesized from simple starting materials
salvage pathways
bases are recovered and attached to an activated ribose
- dominant pathway
how is the purine ring constructed
it is constructed by a series of reactions that add carbons and nitrogen to performed ribose 5-phosphate
Synthesis of purine necleotides
1) Synthesis of 5-phosphoribosyl-1-pyrophosphate (PRPP)
2) Synthesis of 5’-phosphorybosylamine
3) Synthesis of inosine monophosphate (IMP)
azathioprine
immune suppressive cancer drug
- inhibitor of purine synthesis
Hypoxanthine-guanine phosphoribosyltransferase
transfer phosphoribose into ??
leach-nyhan syndrome
- deficiency of HGPRT
1) Increased PRPP and decreased IMP and GMP, increased de novo purine synthesis.
2) Increased breakdown of purine, therefore, increased uric acids.
Sources if purine necleotides
1) Dietary purine
2) Tissue nucleic acids
3) Endogenous purine synthesis
end product of purine nucleotides
uric acids
Adenosine Deamniase
Convert adenosine into inosine
- ADA deficiency causes severe combined immunodeficiency
Adenosine Deaminase Deficiency
does not produce uric acid
leads to deoxyadenosine -> dATP -> ribonucletoide reductase -> inhibition of DNA synthesis with increased T and B cell apoptosis -> severe combined immunodeficiency
Gout
high levels of uric acid in the blood due to under excretion or overproduction of uric acid
Causes of Gout
1) Abnormal PRPP synthetase activity
2) Defect in purine salvage pathway
3) alcohol
Treatment for glout
prevention of the deposition of rate crystals
1) colchine: decrease the movement of the granulocytes into the deposition area
2) allopurinol: analog of hypoxanthine, inhibitor of xanthine oxidase
3) Probenecid and sulfinpyrazone
pyrimidine synthesis
1) formation of carbamoyl phosphate
orotic aciduria
……..
THF(FH4) in AA metabolism
1) degradation of histidine
2) Serine synthesis
3) Resynthesis of methane from homocysteine
primary one carbon carrier
its purpose is to carry and transfer the oxidation state of one carbon unit
