1 / 32

BIOC/DENT/PHCY 230 LECTURE 6

BIOC/DENT/PHCY 230 LECTURE 6. Nucleotides. found in DNA and RNA used for energy (ATP and GTP) building blocks for coenzymes (NADH). Building blocks for nucleotides. Two classes of bases. Two types of ribose. Synthesis of nucleotides.

leroy
Download Presentation

BIOC/DENT/PHCY 230 LECTURE 6

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. BIOC/DENT/PHCY 230 LECTURE 6

  2. Nucleotides • found in DNA and RNA • used for energy (ATP and GTP) • building blocks for coenzymes (NADH)

  3. Building blocks for nucleotides

  4. Two classes of bases

  5. Two types of ribose

  6. Synthesis of nucleotides • nucleotide bases can be recycled or synthesised de novo • purine bases are synthesised on ribose • pyrimidine bases are synthesisedindependent of ribose

  7. AMP Synthesis of PRPP • PRPP contributes ribose phosphate to nucleotides • formation catalysed by PRPP synthetase PRPP synthetase is allosterically inhibited by AMP, ADP and GDP.

  8. De novo purine synthesis Glutamine donates an amide to initiate purine synthesis A whole glycine is added to the nitrogen

  9. The coenzyme tetrahydrofolate donates a formyl group Glutamine donates a second amide

  10. Imidazole ring is closed in an energy dependent reaction

  11. Aspartate is added in an energy dependent reaction This is analogous to the urea cycle

  12. Ring closure Tetrahydrofolate donates a second formyl group

  13. Origins of purine base

  14. IMP can be converted to GMP and AMP

  15. De novo pyrimidine synthesis The pyrimidine base is synthesised before being attached to ribose

  16. ring closure and oxidation

  17. Ribose is now added via PRPP

  18. UMP can be used to synthesise CTP

  19. Origins of pyrimidine base

  20. purines pyrimidines Basesynthesis on ribose free Amino acids gln(2), asp, asp gly Other molecules formate(2) carbamoyl HCO3- phosphate ATP 5 2 (UMP) (AMP,GMP) Comparison of purine and pyrimidine biosynthesis CMP gln 3

  21. Ribonucleotides are used as precursors for deoxyribonucleotides ATP dATP GTP dGTP CTP dCTP UTP dUTP Ribonucleotide reductase

  22. Thymidine nucleotides are derived from dUMP Tetrahydrofolate donates a methyl group

  23. Degradation of pyrimidine nucleotides CTP UTP b-alanine, NH3, CO2

  24. Degradation of purine nucleotides

  25. ATP ADP + Pi 2ADP ATP + AMP AMP IMP + NH4+ AMP deaminase Free ammonia is also produced in muscle • during severe muscle activity

  26. Degradation of purine nucleotides

  27. GOUT • uric acid is quite insoluble • excess uric acid can crystallise in joints • gout can be treated with allopurinol • allopurinol is a competitive inhibitor of xanthine oxidase

  28. The take home message • nucleotides have a number of functions • they can be synthesised de novo if required • some steps are analogous with the urea cycle • amino acids provide many of the components • synthesis is regulated by the concentrations of various nucleotides • synthesis is energetically expensive • the degradation of excess purines can cause gout

More Related