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27 Cards in this Set
- Front
- Back
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What are the three steps in Nucleotide triphosphate formation?
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1. Formation of ATP
2. Formation of NDP 3. Formation of NTP |
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What is the enzyme responsible for ATP formation?
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Adenylate kinase
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What is the enzyme responsible for NDP formation?
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NMP kinase
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What is the enzyme responsible for NTP formation?
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NDP kinase
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What are the specificities associated with NDP kinases?
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Bases specific. Non-specific for sugar.
e.g. - UMP kinase catalyzes UMP + ATP --> UDP + ADP |
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What are the specificities associated with UDP kinase?
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Nonspecific for phosphate donor, base, and suar.
Very promiscuous. |
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What type of nucleotides are required for DNA synthesis?
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deoxyribonucleotides
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Purines and pyrimidines are synthesized as what?
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ribonucleotides
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What enzyme catalyzes the reduction of ribose to deoxyribose?
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Ribonucleotide reductase
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T/F - Ribonucleotide reductase acts on both nucleoside di- and triphosphates.
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True
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What are the subunits of ribonuceotide reductase?
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R1 and R2
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What are the two ways in which ribonucleotide reductase can be regulated?
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1. Overall activity
2. Substrate specificity |
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What are the two regulatory sites of R1 in ribonucleotide reductase?
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1. Primary regulation site controlling overall activity
2. Allosteric site controlling relative levels of each dNTP |
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In terms of ribonucleotide reductase overall activity, where does ATP bind and what effects does it have?
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ATP binds at the primary regulation site on R1.
ATP activates formation of dADP, dCDP, dGDP, and dUDP |
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In terms of ribonucleotide reductase, where does dATP bind and what effects does it have?
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dATP binds at the primary regulation site on R1.
dATP inhibits formation of dADP, dCDP, dGDP, and dUDP |
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In terms of ribonucleotide reductase overall activity, what two molecules are the activators/inhibitors?
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ATP and dATP
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In terms of ribonucleotide reductase substrate specificity, what does ATP do?
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Increase UDP and CDP usage.
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In terms of ribonucleotide reductase substrate specificity, what does dTTP do?
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Increase GDP usage
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In terms of ribonucleotide reductase substrate specificity, what does dGTP do?
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Increase ADP usage.
Decrease GDP, UDP, and CDP usage. |
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T/F - Ribonucleotide reductase uses TDP.
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False. Uses UDP instead.
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What is an inhibitor of Ribonucleotide reductase?
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Hydroxyurea
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Which regulatory mechanism is responsible for ensuring equivalent levels of each dNTP made?
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Substrate specificity site of ribonucleotide reductase
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dTMP is synthesized from what two dNTP's?
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dCTP or dUTP (after conversion to dUMP)
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What prevents incorporation of uracil into DNA?
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dUTPase
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Describe the actions of thymidylate synthase to form dTMP.
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Adds methyl group from THF to dUMP to form dTMP.
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What is an inhibitor of thymidylate synthetase?
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Fluorouracil
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Thymidylate synthesis is also inhibited by what inhibitors of DHFR?
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Methotrexate and sulfa drugs.
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