Download presentation
Presentation is loading. Please wait.
1
Nucleotides metabolism
2
【目的与要求】 记住嘌呤核苷酸有两条合成途径。结合嘌呤核苷酸结构与从头合成途径，说出嘌呤核苷酸各元素或组件的材料来源。熟记二磷酸核苷还原生成脱氧嘌呤核苷酸。写出与嘌呤核苷酸补救合成有关的酶的名称、功能、酶缺陷相关的疾病 结合嘌呤核苷酸合成途径、调节，熟记嘌呤核苷酸抗代谢药物作用机理及临床意义 记住嘌呤核苷酸体内分解代谢终产物-尿酸及其与医学的关系 熟记嘧啶核苷酸从头合成的原料及合成调节。说出嘧啶核苷酸补救合成所需的酶及其催化的反应。明白嘧啶核苷酸抗代谢药物作用机理，记住嘧啶核苷酸分解代谢产物名称
3
Outline 8.1 Purine metabolism -8.1.1 The Biosynthesis of Purines
Purine Salvage De-oxyribonucleotide Synthesis Purine Degradation 8.2 Pyrimidine metabolism Biosynthesis of Pyrimidines Pyrimidine Degradation
4
Nuclear acid digestion
food (stomach) protein nuclear acid (RNA and DNA) (intestine) RNase (phosphodiesterase) Endonucleases DNase mononucleotide ribonucleotide mmol Deoxyribonucleotide umol (phosphoesterase) Nucleotidase nucleoside Phosphate nucleosidase Uric acid (purines) base Ribose or ribose-1-phosphate β-ureidopropionate ( primidines) (戊糖代谢) excrete
5
Biological Roles of Nucleotides
Monomeric units of nucleic acids * “ Energy currency”(ATP) * Regulation of physiological processes Adenosine controls coronary(冠脉) blood flow cAMP and cGMP serve as signaling molecules Precursor function - GTP to tetrahydrobiopternin Coenzyme components - 5’-AMP in FAD/NAD+ Activated intermediates: UDP-Glucose Allosteric effectors- regulate themselves and others
6
思考？ 利用所学知识，试评价“珍奥核酸”的功能
7
8.1.1 Nucleotide Biosynthesis
For both purines and pyrimidines there are two means of synthesis - de novo (from bits and parts) - salvage (recycle from pre-existing nucleosides,and bases) Ribose generates energy, but purine and pyrimidine rings do not Nucleotide synthesis pathways are good targets for anti-cancer/antibacterial strategies
8
Bases/Nucleosides/Nucleotides Base + Sugar + Phosphate=
Deoxyadenosine 5’-triphosphate (dATP) Adenine Deoxyadenosine
9
The Pyrimidine Ring The Purine Ring
10
Purine
11
Pyrimidine
12
De novo purine biosynthesis
John Buchanan (1948) "traced" the sources of all nine atoms of purine ring 1. In de novo synthesis, Inosine-5'-P (Inosine Monophosphate, IMP) is the first nucleotide formed 2. It is ,then, converted to either AMP or GMP Location: liver cellular Cytoplasm De novo purinenucleotide synthesis proceeds by the synthesis of the purine base upon the ribose sugar moiety
13
The metabolic origin of the nine atoms in the purine ring system
N-1: aspartic acid C-2:THF - one carbon units N-3: glutamine C-4, C-5, N-7: glycine C-6: CO2 C-8: THF - one carbon units N-9: glutamine 甘氨当中站, 谷氮坐两边, 左上天冬氨, 头顶CO2 还有俩一碳 C-6 N-7 C-4 C-5 N-1 C-8 C-2 N-9 H N-3 The metabolic origin of the nine atoms in the purine ring system
14
1. First, synthesis Inosine-5'-P (Inosine Monophosphate, IMP)
15
R-5'-P ATP PRPP synthetase P_ P PP-1'-R-5'-P(PRPP)
16
Figure 5-磷酸核糖胺,PRA T1/2 30s
17
Figure 甘氨酰胺核苷酸(GAR)
18
Figure 甲酰甘氨酰胺核苷酸 (FGAR)
19
Figure 甲酰甘氨咪核苷酸(FGAM)
20
Figure 5-氨基咪唑核苷酸 (AIR)
21
Figure 5-氨基咪唑-4-羧酸核苷酸
22
5-氨基咪唑-4-(N-琥珀酸) -甲酰胺核苷酸(SAICAR)
Figure 5-氨基咪唑-4-(N-琥珀酸) -甲酰胺核苷酸(SAICAR)
23
5-氨基咪唑-4-(N-琥珀酸) -甲酰胺核苷酸(SAICAR)
Figure 5-氨基咪唑-4-(N-琥珀酸) -甲酰胺核苷酸(SAICAR)
24
5-氨基咪唑-4-甲酰胺 核苷酸(AICAR)
Figure 5-氨基咪唑-4-甲酰胺 核苷酸(AICAR)
25
5-甲酰胺基咪唑- 4-甲酰胺核苷酸(FAICAR)
Figure 5-甲酰胺基咪唑- 4-甲酰胺核苷酸(FAICAR)
26
Figure
27
Inosine monophosphate
(2) ATP dependent step ATP dependent step PRPP NH3 via glutamine Inosine monophosphate 1 carbon via folate NH3 via aspartyl- succinate
28
2. Second, Making AMP and GMP
30
ATP AMP ADP GTP GMP GDP kinase kinase kinase kinase ATP ADP ATP ADP
31
Purines are synthesized on the Ribose ring
Committed Steps ( at the first two steps ): PRPP , PRA (A bunch of steps you don’t need to know) 2.End product inhibition and “feed forward” regulation Regulation of De Novo Synthesis 3. “cross regulation” occurs from IMP to AMP and GMP ATP provides the energy for GMP synthesis GTP provides the energy for AMP synthesis Feedback Inhibition
32
Committed Step
33
8.1.2 Salvage Pathway for Purines
Hypoxanthine or Guanine + PRPP = IMP or GMP + PPi Hypoxanthineguanosylphosphoribosyl transferase (HGPRTase) Adenine + PRPP = AMP + PPi Adeninephosphoribosyl transferase (APRTase) A-PRT(phosphoribosyltransferases) is not very important because we generate very little adenine. (the catabolism of adenine nucleotides and nucleosides is through inosine) HG-PRT, though, is exceptionally important and it is inhibited by both IMP and GMP. This enzyme salvages guanine directly and adenine indirectly. Remember that AMP is generated primarily from IMP, not from free adenine PRTs catalyze the addition of ribose 5-phosphate to the base from PRPP to yield a nucleotide Base + PRPP = Base-ribose-phosphate + PPi Salvage pathways are particularly important in brain/marrow that lack de novo purine synthesis
34
Lesch-Nyhan Syndrome(莱-尼综合症)
Absence of HGPRTase X-linked (Gene on X) Occurs primarily in males Characterized by: purine synthesis is increased 200-fold Increased uric acid Spasticity(痉挛) Neurological defects Aggressive behavior Self-mutilation(自残)
35
Inter-conversion of Purine nucleotides
NADP+ NH3 NADPH Guanine Reductase GMP AMP NH3 Adenine Deaminase AMPS （腺苷酸代琥珀酸） IMP XMP
36
8.1.3 Deoxyribonucleotide Biosynthesis
1´ 2´ 3´ 4´ 5´ BASE 1´ 2´ 3´ 4´ 5´ BASE Ribonucleotide Reductase Deoxyribonucleoside Ribonucleoside
37
NDP dNDP ADP dADP GDP dGDP UDP dUDP CDP dCDP TDP dTDP
ribonucleotide reductase NDP dNDP ribonucleotide reductase ADP dADP ribonucleotide reductase GDP dGDP ribonucleotide reductase UDP dUDP ribonucleotide reductase CDP dCDP TDP dTDP
38
Deoxyribonucleotide Biosynthesis ?
硫氧还蛋白 Mg2+ Ribonucleotides can be converted to deoxyribonucleotides by Ribonucleotide Reductase at the diphosphate level
39
Regulates the level of cellular dNTPs
E. coli Ribonucleotide Reductase Regulates the level of cellular dNTPs Highly regulated enzyme Activated prior to DNA synthesis Controlled by feedback inhibition by dATP, and complex positive regulation by TTP, dGTP and dGTP The ribonucleotide reductase, An (R1)2(R2)2- type enzyme , has R1 (86 kD) and R2 (43.5 kD) two subunits
40
? kinase dNTP+ADP dNDP+ATP kinase dADP+ATP dATP +ADP kinase dGDP+ATP
dGTP+ADP kinase dUDP+ATP dUTP+ADP kinase dCTP+ADP dCDP+ATP phosphorylase dNDP dNMP+Pi ? dTTP
41
Regulation of dNTP Synthesis
The overall activity of ribonucleotide reductase must be regulated Balance of the four deoxynucleotides must be controlled ATP activates, dATP inhibits at the overall activity site ATP, dATP, dTTP and dGTP bind at the specificity site to regulate the selection of substrates and the products made
42
Figure 22-40
43
over-growth + Heterogeneity ( nucleotides + protein )
Tumor over-growth Heterogeneity ( nucleotides + protein ) How to inhibit the biosynthesis of the tumor cells? for anti-cancer strategies(antibacterial)
44
Chemotherapeutic Agents
1. Analogs of purine: N OH H N SH H 6-巯基嘌呤 （6-mercaptopurine, 6-MP） inosine N SH H H2N N OH H 8-氮杂鸟嘌呤 (8-azoguanine) 6-巯基鸟嘌呤 (6-mercaptoguanine)
45
2. Analogs of amino acids:
H2N—C—CH2—CH2—CH—COOH O NH2 Gln Inhibit the reactions of the Gln N+ —N—CH2—C—O—CH2—CH—COOH O NH2 氮杂丝氨酸（azaserine） N+ —N—CH2—C—CH2—CH2—CH—COOH O NH2 6-重氮-5-氧正亮氨酸(diazonnorleucine)
46
3. Analogs of Folic acid NH2 R O N —CH2—N— —C—N—CH CH2 H2N
COOH R=H，aminopterin,氨喋呤 R=CH3，methotrexate, 氨甲喋呤,MTX N C H —CH2—N— —C—N—CH O CH2 COOH H2N OH 四氢叶酸,THF
47
6MP MTX PRPP PRA GAR FGAR Gln FGAM 6MP AMP A MTX IMP I GMP G 6MP 6MP
azaserine 氮杂丝氨酸(azaserine) FGAM PPi PRPP 6MP AMP A MTX PPi PRPP AICAR FAICAR IMP I GMP G 6MP azaserine PPi PRPP The mechanism of the Chemotherapeutic Agents 6MP
48
8.1.4 Purine catabolism AMP I Uric Acid X GMP G XO XO
Sequential removal of bits and pieces End product is uric acid XO: Xanthine Oxidase Excreted in Urine
49
Xanthine Oxidase and Gout
＞0.48mmol/L(8mg%), The scale of uric acid (normal value) : 0.12～0.36mmol/L; male, 0.27mmol/L; formale, 0.21mmol/L XO in liver, intestines (and milk) can oxidize hypoxanthine (twice) to uric acid Humans and other primates(灵长类) excrete uric acid in the urine, but most N goes out as urea Gout occurs from accumulation of uric acid crystals in the extremities
50
Allopurinol, which inhibits XO, is a treatment of gout
别嘌呤醇 次黄嘌呤
51
Allopurinol nucleotide
The mechanism of allopurinol as a treatment of gout C OH N H N OH H CH allopurinol PRPP ↓ I XO Allopurinol nucleotide X Purine nucleotides Uric acids
52
8.2 Pyrimidine Biosynthesis
In contrast to purines, First, synthesis of the pyrimidine ring; Next, attachment of ribose-phosphate to the ring
53
The metabolic origin of the six atoms of the pyrimidine ring
De Novo Pyrimidine Biosynthesis NH2 HC H2C HOOC Carbamoyl-P Aspartate The metabolic origin of the six atoms of the pyrimidine ring
54
乳清酸 二氢乳清酸 乳清酸核苷酸
55
UTP UMP UDP kinase kinase CTP From UTP at the triphosphate level ATP
ADP ATP ADP
56
Synthesis of Thymine Nucleotides
1. Thymine nucleotides are made from dUMP, which derives from dUDP, dCDP 2. Biosynthesis of deoxyribonucleotides by ribonucleotide reductase Figure 22-41 3. Biosynthesis of thymidine monophosphate (dTMP) by thymidylate synthase
57
dUMP dTMP dTTP dTMP dTDP
Thymidylate synthase methylates dUMP at 5-position to make dTMP C O HN CH N dR-5'-P C O HN C-CH3 CH N dR-5'-P dTMP synthase N5,N10- methylene FH4 FH2 DHFR FH4 NADP+ NADPH+H+ dUMP dTMP N5,N10-methylene THF is 1-C donor kinase kinase dTTP dTMP dTDP ATP ADP ATP ADP
58
Regulation of Pyrimidine Synthesis（de novo）
Aspartate transcarbamoylase (ATCase，细菌) catalyzes the condensation of carbamoyl phosphate with aspartate to form carbamoyl-aspartate Note that carbamoyl phosphate represents an ‘activated’ carbamoyl group Feedback Inhibition
59
× Feedback Inhibition Regulation of Pyrimidines Biosynthesis
Regulation occurs at first step in the pathway (committed step) Inhibited by UTP If you have lots of UTP around this means you won’t make more that you don’t need Feedback Inhibition × 2ATP + CO2 + Glutamine = carbamoyl phosphate
60
CPS II Carbamoyl phosphate for pyrimidine synthesis is made by carbamoyl phosphate synthetase II (CPS II，哺乳动物细胞) This is a cytosolic enzyme (whereas CPS I is mitochondrial and used for the urea cycle) Substrates are HCO3-, glutamine, 2 ATP
61
Allosteric regulation of pyrimidine biosynthesis
Enzyme regulated Allosteric effector Effect carbamoyl phosphate synthetase II UDP, UTP Feedback inhibition PRPP, ATP stimulatory
62
CPS-I vs. CPS-II ?
63
Biosynthesis: Purine vs. Pyrimidine
start with ribose, build on nitrogen base Regulated by GTP/ATP Generates IMP Requires Energy build nitrogen base then added to PRPP Synthesized Regulated by UTP Generates UMP/CMP Requires Energy “Both are very complicated multi-step process which your kindly professor does not expect you to know in detail”
64
Salvaging Pyrimidines
Pyrimidines+PRPP Nucleoside+PPi (嘧啶磷酸核糖转移酶) A second type of salvage pathway involves two steps and is the major pathway for the pyrimidines, uracil and thymine Base + Ribose 1-phosphate = Nucleoside + Pi (nucleoside phosphorylase) Nucleoside + ATP Nucleotide + ADP (nucleoside kinase-irreversible) Uridine + ATP UMP + ADP; uridine kinase Nucleoside phosphorylase/kinase: U,C,T + ribose 1-P nucleosides + Pi Thymine + deoxyribose-1-P thymidine + Pi; thymine phosphorylase Thymine + ATP dTMP + ADP; thymidine kinase Thymidine kinase activity changes during cell cycle; very active during DNA synthesis and is inhibited by dTTP
65
Analogs of pymidines /pymidine nucleosides:
Inhibitors of pymidines synthesis are cancer drugs Analogs of pymidines /pymidine nucleosides: HOH2C H OH O C N NH·HCl HOH2C H HO OH O C N NH2 N H O F 5-氟尿嘧啶, 5-Fu 环胞苷 Cyclocytidine 阿糖胞苷 Cytarabine
66
UMP UTP CTP CDP dCDP MTX dTMP UDP dUDP dUMP 5FU
氮杂丝氨酸 azaserine 阿糖胞苷Cytarabine UMP UTP CTP CDP dCDP MTX dTMP UDP dUDP dUMP 5FU (5FdUMP/5FUTP)
67
Pyrimidine Catabolism-1
CH NH2 H C O HN CH N H C O HN CH2 N H NADPH+H+ NADP+ NH3 H2O C U C O H2N CH2 N H HO CO2+NH3 β-Alanine H2O H2N-CH2-CH2-COOH
68
Pyrimidine Catabolism-2
HN C-CH3 CH N H C O HN CH-CH3 CH2 N H NADPH+H+ NADP+ DHT T H2O Pyrimidine Catabolism-2 C O H2N CH-CH3 CH2 N H HO CO2+NH3 H2O H2N-CH2-CH-COOH CH3 β-氨基异丁酸 β-aminoisobutyrate β-脲基异丁酸
69
overview De novo synthesis 5'-P-R CO2+Gln PRPP H2N-CO-P IMP OMP AMP
dAMP dGMP GMP UMP dUMP dUMP CMP dCMP dCMP dTMP ADP dADP dGDP GDP UDP dUDP dUDP CDP dCDP dTDP dUTP ATP dATP dGTP GTP UTP CTP dCTP dTTP De novo synthesis
70
CPS-I vs. CPS-II 分布 线粒体(肝) 胞液 氮源 氨 谷氨酰胺 变构激活剂 N-乙酰谷氨酸 无 变构抑制剂 无 UMP 功能
尿素合成 嘧啶合成
Similar presentations
