Nucleotide Metabolism2555
Chalermchai Mitrpant
OutlineOutline• Structure of nucleotide
• Biosynthesis of pyrimidine nucleotide
• Function of nucleotide
• Biosynthesis of purine nucleotide
De novo and Salvage pathway and its regulatory mechanism
De novo and Salvage pathway and its regulatory mechanism
• Diseases relating to nucleotide synthesis
• Biosynthesis of deoxynucleotide and its regulatory mechanism
• Catabolism of pyrimidine nucleotide and related diseases
• Catabolism of purine nucleotide and related diseases
• Biosynthesis of Coenzymes
• Medication related to nucleotide metabolism
Structure and function of NucleotideStructure and function of Nucleotide
Structure of NucleotideStructure of Nucleotide
Function of NucleotideFunction of Nucleotide
1. เปนหนวยยอย (monomeric unit) ใชในการสรางกรดนิวคลีอิคซึ่งในรางกายแบงไดเปน 2 พวก คือ DNA (deoxyribonucleic acid) และ RNA (ribonucleic acid)
2. Adenosine triphosphate (ATP); เปนสารใหพลังงานสงู มีความสําคัญ ในการขับเคลื่อนปฏิกิริยาตางๆที่จําเปนตองใชพลงังาน โดยปฏิกิริยาสลาย ATP (ATP hydrolysis) จะสงผานพลังงานเสรี เพื่อเปลี่ยนสมดุลของปฏิกิริยาใหัเกิดไดงายขึ้น (ATP coupling)
3. เปนสื่อกลาง (mediator) ของขบวนการตางๆในรางกาย เชน cyclic AMP (cAMP), cyclic GMP (cGMP)
4. เปนสารตนในการสังเคราะห cofactor บางชนิด เชน GTP ใชในการสังเคราะห tetrahydrobiopterin
5. เปนสวนประกอบของโคเอนไซม เชน NAD (nicotinamide adenine dinucleotide), FAD (flavin adenine dinucleotide) และ coenzyme A
Function of NucleotideFunction of Nucleotide
6. ชวย นํา สาร intermediates ในปฏิกิริยาบางอยาง เชน UDP‐glucose (Glycogen synthesis), CDP‐choline, และ CDP‐diacylglycerol (glycolipid synthesis), 7‐methylguanosine triphosphate (RNA modification)
7. เปน allosteric effector ที่ควบคุมการทํางานของเอนไซมหลายชนิด
8. AMP ทําหนาที่ metabolic sensor ควบคุมเมแทบโบลิซึมในเซลล ทํางานสัมพันธกันกับ adenylate kinase (AK) และ AMP kinase (AMPK)
9. ADP ทําหนาที่เกี่ยวของกบัการเกาะกลุมของเกล็ดเลอืด ภายหลังจากเกล็ดเลอืดถูกกระตุน จะหลั่ง ADP และ ADP นี้เองจะจับกับ adenosine receptor P2Y12 บนผิวของเกลด็เลือดนํา ไปสูการเกาะกลุมของเกล็ดเลอืด
AMP as a metabolic sensorAMP as a metabolic sensor
ADP
Clopidogrel
ADP as a mediator for platelet activationADP as a mediator for platelet activation
BiosynthesisBiosynthesis
Biosynthesis of nucleotideBiosynthesis of nucleotide
Purine nucleotide Pyrimidine nucleotide
• De no vo
• Salvage
• De no vo
• Salvage
Synthesis of PRPPSynthesis of PRPP
Voet Biochemistry 3e© 2004 John Wiley & Sons, Inc.
The metabolic pathway for the de novo The metabolic pathway for the de novo biosynthesis of IMPbiosynthesis of IMP
Voet Biochemistry 3e© 2004 John Wiley & Sons, Inc.
IMP is converted to AMP or GMP in IMP is converted to AMP or GMP in separate two reactionsseparate two reactions
Voet Biochemistry 3e© 2004 John Wiley & Sons, Inc.
The biosynthetic origins of purine ring atomsThe biosynthetic origins of purine ring atoms
IMP
De novo Purine synthesisDe novo Purine synthesis
Voet Biochemistry 3e© 2004 John Wiley & Sons, Inc.
IMP is converted to AMP or GMP in IMP is converted to AMP or GMP in separate two reactionsseparate two reactions
Regulation of de novo Purine synthesisRegulation of de novo Purine synthesis
Salvage purine synthesisSalvage purine synthesis
Salvage purine synthesisSalvage purine synthesis
De novo Pyrimidine synthesisDe novo Pyrimidine synthesis
Salvage pyrimidine synthesisSalvage pyrimidine synthesis
Biosynthesis of deoxynucleotideBiosynthesis of deoxynucleotide
Substrate for RNA synthesis
Deoxyadenosine triphosphate dATP
dGTP
dCTP
dTTP
Substrate for DNA synthesis
Biosynthesis of deoxynucleotideBiosynthesis of deoxynucleotide
Biosynthesis of deoxynucleotideBiosynthesis of deoxynucleotide
Substrate for RNA synthesis
Deoxyadenosine triphosphate dATP
dGTP
dCTP
dTTP
Substrate for DNA synthesis
dUTP
Biosynthesis of deoxynucleotideBiosynthesis of deoxynucleotide
Regulation of ribodinucleotide reductaseRegulation of ribodinucleotide reductase
Diseases related to biosynthesis of nucleotideDiseases related to biosynthesis of nucleotide
Purine Pyrimidine
1. Lesch nyhan syndrome 1. Orotic aciduria
2. Renal lithiasis (APRT deficiency)
Lesch Nyhan syndromeLesch Nyhan syndrome
• X-linked recessive inherited disorder • Neurological dysfunction
• Cognitive and behavioral disturbance; self-mutilation
• Uric acid overproduction
How does Lesch Nyhan syndrome causes hyperuricemia
• Excess of hypoxanthine and guanine
• Reduced IMP and GMP
• Excess of PRPP
Management• Symptomatic treatment; benzodiazepine (reduced anxiety)
• Medication to reduce uric acid; Allopurinol & Probenecid
• SAM supplement (still in clinical research)
Lesch Nyhan syndromeLesch Nyhan syndrome
Guanine Deaminase
How does Lesch Nyhan syndrome How does Lesch Nyhan syndrome causes hyperuricemiacauses hyperuricemia
How does Lesch Nyhan syndrome How does Lesch Nyhan syndrome causes hyperuricemiacauses hyperuricemia
Role of SAM supplement in Role of SAM supplement in patient with Lesch Nyhan syndromepatient with Lesch Nyhan syndrome
APRT deficiencyAPRT deficiency
Excess adenine
8-hydroxy adenine
2,8-dihydroxy adenine
Xanthine oxidase
Xanthine oxidase
• Renal lithiasis
• Renal failure
Orotic aciduriaOrotic aciduria
• Orotate decarboxylase or Orotate Phosphoribosyltransferase
• Growth Retardation
• Megaloblastic anemia
Symptoms
Management
• Uridine supplement
• Autosomal recessive
CatabolismCatabolism
Catabolism of purine nucleotideCatabolism of purine nucleotide
Catabolism of purine nucleotideCatabolism of purine nucleotide
Diseases related to catabolism of purineDiseases related to catabolism of purine
2. Severe combined immune deficiency (Adenosine deaminase)
1 .Purine nucleotide phosphorylase
3. Gout
Purine nucleotide phosphorylase deficiencyPurine nucleotide phosphorylase deficiency
• Defect in T-lymphocyte related immunological defense(2/3 of cases)
• Excess 1,2 & 3 can be excreted by kidney
• Excess of 1. inosine, 2. deoxyinosine, 3. Guanosine and 4. deoxyguanosine
• Deoxyguanosine -------> dGTP
Purine nucleotide phosphorylase deficiencyPurine nucleotide phosphorylase deficiency
dGTP
Purine nucleotide phosphorylase deficiencyPurine nucleotide phosphorylase deficiency
dATP
Overall Inhibition of RNR
Inhibit DNA synthesis
Specific activation of RNR
Loss in mitochondrial membrane potential
Apoptosis of thymocyte in Thymus
Effect on number and function of T‐lymphocyte
Adenosine deaminase deficiencyAdenosine deaminase deficiency
• Defect in both T- and B-lymphocyte related immunological defense
• Excess deoxyadenosine -------> dATP
• Severe combined immunodeficiency (SCID)
• Inhibit RNR and inhibit Lymphocyte proliferation
Adenosine deaminase deficiencyAdenosine deaminase deficiency
Hyperuricemia and GoutHyperuricemia and Gout
• Uric; Final degradative product of purine in human
• Deposition of urate crystal causes Gout (Gouty arthritis)
• Not well-dissolved in water
• Increased purine synthesis
• Increased purine catabolism; patient with cancer prescribed on chemotherapy
• Genetic disease; Lesch Nyhan syndrome and PRPS hyperactivity
• Decreased Excretion
Cause of HyperuricemiaCause of Hyperuricemia
• Glucose-6-phosphatase deficiencyExcess G-6-P promotes Pentose phosphate pathway
• Polymorphism on urate transporter ATP binding G2 (ABCG2) decreases rate of urate transport and then decrease urate secretion
Catabolism of purine nucleotide Catabolism of purine nucleotide and uric acid excretionand uric acid excretion
Voet Biochemistry 3e© 2004 John Wiley & Sons, Inc.
Mechanism of competitive inhibitor of Allopurinol on xanthine oxidase
Catabolism of pyrimidine nucleotide Catabolism of pyrimidine nucleotide
1. 5’-Nucleotidase deficiency
2. Lead poisoning
Diseases related to catabolism of pyrimidineDiseases related to catabolism of pyrimidine
Disease relating to Catabolism of pyrimidineDisease relating to Catabolism of pyrimidine
5’‐Nucleotidase deficiency
Hemolytic anemia
Basophilic strippling
Nucleotidase
PNP
Increased CMP and UMP
Features is similar to lead poisoning associated hemolytic anemia
How can lead inhibit 5’Nucleotidase?
Decreased 5’‐Nucleotidase activityIn patient with lead poisoning
55’’--Nucleotidase inhibition in Lead poisoning Nucleotidase inhibition in Lead poisoning
Medications related to nucleotide metabolismMedications related to nucleotide metabolismand coenzyme synthesisand coenzyme synthesis
Antitumour drug in clinical usedAntitumour drug in clinical used1. Antimetabolite
• 5 Fluorouracil (5‐FU)
• 6 Mercaptopurine (6‐MP)
• Inhibit Thymidylate synthase (dUMP dTMP)
2. Antifolate
• Metrothexate• Aminopterin
• Interfere on gene splicing
• DNA damage
• Inhibit Amidophosphoribosyl transferase
• Inhibit IMP dehydrogenase
• Inhibit Adenylosuccinate synthetase
Inhibit Thymidylate synthase (dUMP dTMP)
Tetrahydrofolate
Mechanism of action of Mechanism of action of Antimetabolite and antifolateAntimetabolite and antifolate
Mechanism of action of 6Mechanism of action of 6--MPMP
Antitumour drug in clinical usedAntitumour drug in clinical used3. Glutamine antagonist
• Inhibit reactions required glutamine
• IMP GMP conversion
• UTP CTP conversion
• PRPP synthesis and CPSII
Antiproliferation drugAntiproliferation drug
Hydroxyurea
Antiviral drugAntiviral drug
Acyclovir (Acycloguanosine)
• Active form “Acycloguanosine triphosphate”
• AcycloGTP is the specific substrate for HSV DNA polymerase causing DNA chain termination
• Metabolised to AcycloGMP only by Thymidine kinase of HSV (herpes simplex virus)
• Treatment for Herpes Zoster
Antiviral drugAntiviral drug
AZT (Zidovudin)
• Active form “AZT triphosphate”
• Inhibitory effect of AZT triphosphate on HIV DNA polymerase is 100 fold more sensitive than human DNA polymerase
• Metabolised to AcycloGMP by Thymidine kinase of host cell
• Treatment for Human immune deficiency viral infection
Biosynthesis of Nicotinamide Biosynthesis of Nicotinamide adenine dinucleotideadenine dinucleotide
Biosynthesis of flavin adenine dinucleotideBiosynthesis of flavin adenine dinucleotide
Biosynthesis of Coenzyme ABiosynthesis of Coenzyme A