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Nucleotide metabolism

Chapter 10. Nucleotide metabolism. Function of neucleotides. Precursors for RNA and DNA synthesis Energy substance in body (ATP) Physiological Mediators (cAMP) Components of coenzymes (NAD + ) Allosteric effectors and donor of phosphate group ( phosphorylation )

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Nucleotide metabolism

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  1. Chapter 10 Nucleotide metabolism

  2. Function of neucleotides • Precursors for RNA and DNA synthesis • Energy substance in body (ATP) • Physiological Mediators (cAMP) • Components of coenzymes (NAD+) • Allosteric effectors and donor of phosphate group (phosphorylation) • Formation of activated intermediates UDP-glucose, CDP-choline

  3. Section 10.2 Nucleotide Synthesis and Degradation

  4. Nucleoprotein Protein Nucleic acid Nucleases Nucleotide Nucleotidase Absorption Phosphate Nucleoside Nucleosidase Base Ribose Digestion and absorption of nucleotide Blood

  5. Metabolism of Purine nucleotides • Biosynthesis of purine nucleotides de novo synthesis 从头合成 salvage pathway 补救合成 AMP GMP

  6. CO2 Glycine Aspartate One carbon unit One carbon unit Glutamine 1.De novo synthesis of purine nucleotides

  7. Characteristics of de novo synthesis of purine nucleotides 1. in cytosol 2. form IMP first, then synthesize AMP and GMP from IMP. 3. formation of purines is based on the ribosyl group of 5’-phosphoribose

  8. AMP ATP PRPPK Gln Glutamine PRPP amidotransferase (GPRT) Glu AMP GMP PP-1-R-5-P（ 5’-phosphoribose 1’-pyrophosphate, PRPP） R-5-P （5’-phosphoribose） H2N-1-R-5´-P （5´-phosphoribosyl-amine） Gly, one carbon units, Gln, CO2, Asp involved step by step 磷酸核糖焦磷酸 IMP

  9. _ _ _ + + R-5-P PRPPK GPAT IMP _ ATP GMP GTP XMP GDP _ Adenyl-succinate ADP ATP AMP _ + + _ Regulation of de novo synthesis of purine nucleotides PRPP PRA Adenyl-succinate GTP ATP AMP ADP IMP XMP GTP GMP GDP ATP

  10. 2. Salvage synthesis of purine nucleotides • Material: PRPP, purine (conjunction) nucleosides (phosphorylation) • Location: brain and bone marrow or

  11. APRT adenine+PRPP AMP + PPi HGPRT hypoxanthine+PRPP IMP + PPi HGPRT guanine+PRPP GMP + PPi Adenylate kinase adenosine AMP ATP ADP APRT: adenine phosphoribosyltransferase HGPRT: hypoxanthine-guanine phosphoribosyltransferase

  12. Degradation of purine nucleotides nucleotide nucleosides ribose-1-phosphate purine salvage pathway uric acid Nucleotidase Nucleoside phosphorylase 尿酸

  13. IMP Neucleo-tidase Excretion

  14. Metabolism of pyrimidine nucleotides • Biosynthesis of pyrimidine nucleotides de novo synthesis salvage pathway

  15. 1.De novo synthesis of pyrimidine nucleotides 4 Glutamine 3 5 Aspartate CO2 2 6 1

  16. Characteristics of de novo synthesis of pyrimidine nucleotides 1. mostly in cytosol 2. form UMP first, then synthesize other pyrimidine nucleotides from UMP. 3. in the synthesis of UMP, pyrimidine ring is formed first , then combined with PRPP.

  17. Process of de novo synthesis of UMP • 1. formation of Carbamoyl phsphate (CP) CO2 + glutamine + H2O + 2ATP Carbamoyl phosphate synthaseⅡ (CPSⅡ) O O~PO32- + 2ADP + Pi H2N C carbamoyl phosphate

  18. The different between Carbamoyl phosphate synthaseⅠ,Ⅱ Mitochondria of liver cells cytosol of all cells Location Source of nitrogen NH3 Glutamine N-acetylglutamate None Activator Formation of pyrimidine Function Formation of urea

  19. O O~PO32- H2N C carbamoyl phosphate 2. Formation of UMP + Aspartate Carbamoyl aspartate Orotate乳清酸 PRPP UMP

  20. CTP synthase UMPK NDK ATP ADP Gln ATP ATP ADP Glu ADP dUDP dCMP dTMP dUMP TMP synthase 3. Synthesis of CTP, dTMP or TMP UDP UTP

  21. + - - Purine nucleotides + - Pyrimidine nucleotides Regulation of de novo synthesis of pyrimidine nucleotides ATP + CO2+ glutamine • Activated by substrates • Inhibited by products Carbamoyl phosphate - aspartate Carbamoyl aspartate ATP + 5-phosphate ribose PRPP UMP UTP CTP -

  22. Uracil phosphate ribosyltransferase Uracil +PRPP UMP+ PPi Uridine kinase Uridine+ ATP UMP +ADP Uridine phosphorylase Uracil+ 1-phosphoribose Uridine + Pi Salvage pathway of pyrimidine nucleotides

  23. Degradation of pyrimidine nucleotides nucleotide nucleosides phosphoribose pyrimidine Nucleotidase Nucleoside phosphorylase

  24. Thymine β-ureidoisobutyrate H2O β-aminoisobutyrate Excreted in urine Succinyl CoA Glucose TAC Cytosine NH3 Uracil dihydrouracil H2O + + CO2 + NH3 β-alanine liver Acetyl CoA Urea TAC

  25. dNDP NDP Deoxyribonucleotide biosynthesis Ribonucleotide reductase kinase dNDP+ATP dNTP + ADP

  26. Kinase Kinase ATP ADP ATP ADP Kinase Kinase XMP XDP XTP YTP YDP YTP YDP Biosynthesis of NDP and NTP AMP ADP ATP

  27. Section 10.3 Dysmetabolism of nucleotides and antimetabolites

  28. Dysmetabolism of nucleotides • Caused by the genetic defect or regulatory abnormality of some enzymes participating nucleotide metabolism. Gout（痛风）：pain and tenderness, redness, heat, swelling and joint inflammation Causes：too much uric acid forms crystals in joints and cause inflammation

  29. Risk Factors • Obesity/being overweight • more common in men than women • Certain medicines • Certain foods and alcoholic beverages • Genetics • Enzyme defect

  30. Medication • xanthine-oxidase inhibitors, 黄嘌呤氧化酶抑制剂 allopurinol别嘌呤醇 • uricosurics, 促尿酸尿剂 • urate oxidases尿酸氧化酶

  31. Limit your consumption of certain types of meat：beef, pork, lamb, and “organ meats” (such as liver, kidney, and brain), as well as meat extracts and gravies. • Reduce or eliminate alcohol consumption, especially beer. • Reduce your use of oatmeal, dried beans, spinach, asparagus, cauliflower, and mushrooms • High consumption of seafood is associated with an increased risk of gout.

  32. Antimetabolites • The analogs of ribonucleotide metabolite intermediates synthesized artificially. • Can interfere, inhibit and block the ribonucleotide metabolism. • Used as drugs.

  33. Purine ribonucleotide metabolite analogs 6-mercaptopurine(6-MP) Hypoxanthine (6-MP)

  34. Pyrimidine ribonucleotide metabolite analogs : 5-fluorouracil(5-FU), (T) (5-FU)

  35. NAD+ AMP

  36. Biological oxidation • Respiratory Chain and its composition ，How many Respiratory Chain in the mitochondria? What is the sequence of them? • Oxidation Phosphorylation and the mechanism of it • the regulation of it (Cyanide)? • P/O ratio • How many ATP produced by Respiratory Chain? How to use cytosolic NADH ? • energy-rich compounts

  37. Protein catabolism • Nitrogen Balance, Essential Amino Acids , Complementary effect, Putrefaction, Amino acid metabolic pool, Ketogenic amino acids, Ketogenic and glucogenic amino acids. • deamination, decarboxylation key enzymes, main pathway, main products

  38. ALT, AST(function) • SAM, PAPS, GSH, Dopamine , creatine phosphate (function, formation) • Ammonia, One Carbon Units carrier, source, utilization • Hyperammonemia, PKU, Albinism damage, mechanism

  39. Nucleotide metabolism • Function of neucleotides • de novo synthesis of purine and pyrimidine nucleotides material, character, main steps, • Salvage pathwayof purine and pyrimidine • Degradationof purine and pyrimidine nucleotides products ，Gout • Deoxyribonucleotide biosynthesis

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