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5 Written questions

5 Matching questions

  1. Anti retrovirals
  2. Phophoribosyl transferases PRTs
  3. Origins of Pyrimidine Ring Atoms
  4. How to take Ribonucleosides from Mono, Di and tri phosphate
  5. Purine biosynthesis IMP to AMP
  1. a Adenylate Kinase takes ATP and AMP to 2 ADPs

    nucleoside monophosphate kinases take G,C,UMPs plus ATP to ADP plus G,C,UDPs

    nucleoside diphosphate kinases take G,C,UDPs plus ATP to ADP plus G,C,UTPs

    oxidative phosphorylation takes ADP plus Pi to ATP
  2. b Used for salvage

    Hypoxanthine Guanine PRT or HGPRT catalyzes 2 rxns

    PRPP and hypoxanthine to IMP plus PPi

    or PRPP plus Guanine to GMP plus PPi

    Adenine PRT , APRT

    PRPP plus adenine to AMP plus PPi.
  3. c AZT, DDC, ddI
    Used to treat HIV and AIDS
    Triphosphates inhibit retroviral reverse transcriptase
  4. d N1, C4,5,6= all from Aspartate
    C2, N3 = all from Carbamoyl phosphate
  5. e IMP uses Aspartate and GTP to add N in place of carboxyl O at top

    Fumarate leaves leaving just NH2 and AMP is formed

5 Multiple choice questions

  1. Signs and Symptoms young with hematuria, megaloblastic anemia, hyperuricemia, crystals in urine, mental retardation, decreased gross motor function, and self mutilation, gout in early 20s

    is a Rare X linked disorder 1/400000 males, milder form = 8% kelly-seegmiller syndrome

    Cause = near total deficiency of HGPRT about 2% of activity

    biochemical consequenses
    Overproduction or urate
    Elevated PRPP concentrations
    Marked increase in rate of de novo purine biosynth
  2. 6 mercaptopurine
    6 thiaguanine
    These compounds compete with hypoxanthine and guanine for the salvage enzyme HGPRT.
    They are converted by HGPRT into respective ribonucleotides, they inhibit the committed step of de novo purine biosynthesis pathway catalyzed by Gln PRPP amidotransferase, an effect similar to allopurinol
    They are also incorporated into DNA and RNA
  3. Antivirals, acyclovir, Arabinosyladenine araA, for HSV and herpes related viral encephalitis
    Anti retrovirals, AZT, DDC, ddI for HIV
    Anti neoplastics, arabinosylcytosine araC
    Anti Leukemics, 6 mercaptopurin, 6 thiaguanine
  4. Acyclovir, used to treat HSV infections, and is converted to triphosphate by enzymes including a viral nucleoside kinase with broad substrate specificity, and interferes with DNA synthesis in infected cells

    AraA tx for herpes related viral encephalitis. this is converted to triphosphates interferes with DNA synthesis, and is deaminated rapidly in vivo by ADA so is sometimes administered with a ADA inhibitor
  5. it is similar to dUMP and acts as a suicide inhibitor or thymidylate synthetase TS. This kill rapidly dividing cells Tumors and immune cells

5 True/False questions

  1. Prokaryotic Regulation of Pyrimidine BiosynthCTP inhibits two enzymes

    CTPS which forms CTP from UTP is inhibited by CTP, also it requires GTP so low GTP will slow CTP formation

    CPS II is the first reaction which forms carbamoyl P, and is inhibited by CTP

          

  2. Tx of Gout with Allopurinolserum urate decraeases
    serum hypoxanthine and xanthine increase, these are more soluble and easily excreted
    Decreases total rate of purine biosynthesis

          

  3. Effects of Allopurinol Tx on LNS ptsReduces urate in LNS pts by blocking xanthine oxidase rxns

    Ineffective in reducing rate of de novo purine biosynthesis, since it cannot synthesize allopurinol ribonucleotide from allopurinal and PRPP, it requires HGPRT

    Can have neurological effects due to the brains reliace on salvage pathways for most purine nucleotide production and needs GTP for dopamine formation

          

  4. Nucleoside Phosphorylasessome discussed earlier
    araC, triphosphate interferes with DNA synthesis

          

  5. Biochemical Consequenses of ADA deficiencyanother rare cause of SCIDS Disorder, since Ino, dIno, Guo and dGuo are strong subtrates of PNP and Ado and dAdo is weak we get a larger build up of dAdo relative to dNTPs

          

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