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5 Written questions

5 Matching questions

  1. Hypoxanthine
  2. Why IMP to GMP uses ATP
  3. Third step in Pyrimidine biosynth Dihydroorotase
  4. Common thread
  5. Phophoribosyl transferases PRTs
  1. a the base on IMP
  2. b this is a way to use biofeedback high ATP means GMP should be formed Low ATP means ATP should be formed
  3. c Clinical use of nucleotide analogs usually is restricted to bases and nucleoside since phosphorylated nucleotides are poorly transported into cells

    They rely on tricking cellular or viral enzymes into phosphorylating nucleosides into metabolically active nucleotide forms, or converting bases into nucleotides vis salvage pathways
  4. d 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.
  5. e Ring closure no ATP

    Forms Di hydroorotase

    after NAD+ forms to orotate

5 Multiple choice questions

  1. Removes CO2 and forms Uracil base on ribose P, UMP from OMP
  2. this is a way to use biofeedback high GTP means AMP should be formed Low GTP means GMP should be formed
  3. CPS II = takes CO2 and Gln to Carbamoyl P
    ATCase, committed step = take Carbamoyl P and Aspartate to N-Carbamoyl aspartate
    CTPS = takes UTP to CTP
  4. some discussed earlier
    araC, triphosphate interferes with DNA synthesis
  5. Used for degradation

    Purine Nucleoside Phosphorylase has multiple substrates. Has a stronger affinity for Guo and Ino, and weak affinity for Ado, all are not phosphorylated

    It takes them all to Guanine, hypoxanthine, and adenine pluse a ribose 1 phosphate

5 True/False questions

  1. Prokaryotic Regulation of Pyrimidine BiosynthCTP inhibits the action of ATCase the committed step and addition of aspartate to carbamoyl P

    and UMP inhibits the action of CPSII the first step and formation of Carbamoyl p


  2. Anti Leukemics6 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. Tx of Gout with AllopurinolAllopurinol is a suicide inhibitor of xanthine oxidase, because it is similar in configuration to hypoxanthine and it binds tightly to molybdenum in xanthine oxidase.

    Xanthine oxidase takes Hypoxanthine to xanthine and xanthine to uric acid


  4. Second Step in Pyrimidine biosynth ATCaseCommitted Step, and an allosteric enzyme

    Using Aspartate Transcarbamoylase, ATCase takes Carbamoyl Phosphate to N-carbamoyl aspartate adding aspartate


  5. Primary Genetic basis of GoutPurine biosynthesis regulation and secondary causes

    Increased activity of PRPP synthetase increases conc of PRPP

    Increased activity of PRPP amido transferase

    also Partial loss of activity of HGPRT salvage enzyme


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