Chapter 20 Nitrogen Metabolism:

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Chapter 20 Nitrogen Metabolism Purines and
Pyrimidines
Purines
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• Starts with ribose-5-P from the
• pentose phosphate pathway
• Inosine-5-phosphate is synthesized
• using, in part, 1C units requiring folic acid.

3. Reactions involving tetrahydrofolate are
targets for chemotherapeutic agents.
methotrexate.
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4. Inosine monophosphate (IMP) is an
important intermediate in the synthesis of
both adenine guanine nucleotides.
5. Energy is required
6. The process is under feedback regulation
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Catabolism of purine nucletodes

• RNA is degraded to AMP and GMP
• The phosphate is removed
• The base is degraded.

Or The Salvage pathway Base is reused.
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Pyrimidine Synthesis The bases are synthesized
first and then attached to the sugars.
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How are deoxyribonucleotides made?

• Ribonucleotide diphosphates are redicued
• to deoxyribonucleoside diphosphates.

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2. The conversion of uridine to thymidine.
Tetrahyhdrofolate