Biosynthesis and Degradation of Nucleotides ©Copyright 1999-2004 by Gene C. Lavers No part of this presentation may be reproduced by any mechanical, photographic,

Biosynthesis and Biosynthesis and Degradation of Degradation of Nucleotides Nucleotides

Biosynthesis and Biosynthesis and Degradation of Degradation of Nucleotides Nucleotides

©Copyright 1999-2004 by Gene C. Lavers

No part of this presentation may be reproduced by any mechanical, photographic, or electronic process, or in the form of a phonographic recording, nor may it be stored in a retrieval system, transmitted, or otherwise copied for public or private use, without written permission from the publisher.

©Copyright 1999-2004 by Gene C. Lavers

No part of this presentation may be reproduced by any mechanical, photographic, or electronic process, or in the form of a phonographic recording, nor may it be stored in a retrieval system, transmitted, or otherwise copied for public or private use, without written permission from the publisher.

Lecture 42-43Lecture 42-43Baynes & Dominiczak, Baynes & Dominiczak, Chapter 28Chapter 28

Gene C. Lavers, Ph.D.Gene C. Lavers, [email protected]@nyu.edu

Lecture 42-43Lecture 42-43Baynes & Dominiczak, Baynes & Dominiczak, Chapter 28Chapter 28

Gene C. Lavers, Ph.D.Gene C. Lavers, [email protected]@nyu.edu

©Copyright 1999-2004 by Gene C. Lavers, Ph.D.

2

Purine and Pyrimidine Purine and Pyrimidine Nucleic Acid Nucleic Acid MetabolismMetabolism Parent heterocyclic compoundsParent heterocyclic compounds

Purine and Pyrimidine Purine and Pyrimidine Nucleic Acid Nucleic Acid MetabolismMetabolism Parent heterocyclic compoundsParent heterocyclic compounds

Fig. 28.1 Structure of purines and pyrimidines.Fig. 28.1 Structure of purines and pyrimidines.Fig. 28.1 Structure of purines and pyrimidines.Fig. 28.1 Structure of purines and pyrimidines.

©Copyright 1999-2004 by Gene C. Lavers, Ph.D.

3

Purine and Pyrimidine Family Purine and Pyrimidine Family Nucleic Acid Nucleic Acid MetabolismMetabolism Bases, nucleosides, nucleotidesBases, nucleosides, nucleotides

Purine and Pyrimidine Family Purine and Pyrimidine Family Nucleic Acid Nucleic Acid MetabolismMetabolism Bases, nucleosides, nucleotidesBases, nucleosides, nucleotides

NN99-H -H N N–– + H + H++ basic N basic N Purines and pyrimidines are semi-Purines and pyrimidines are semi-

aromatic ring systemsaromatic ring systems bonds similar to benzenebonds similar to benzene Bases stack verticallyBases stack vertically

Ribose in RNA; deoxyribose in DNARibose in RNA; deoxyribose in DNA (d)(d)Base-sugar = Base-sugar = (d)(d)nucleosidenucleoside

(d)(d)Base-sugar-POBase-sugar-PO44== = = (d)(d)nucleotidenucleotide

Base-pairsBase-pairs A A = = T or T T or T = = A AA A==U or UU or U==A A

C C G or G G or G CC

A C G U are in RNAA C G U are in RNA dA dC dG dT are in DNAdA dC dG dT are in DNA

NN99-H -H N N–– + H + H++ basic N basic N Purines and pyrimidines are semi-Purines and pyrimidines are semi-

aromatic ring systemsaromatic ring systems bonds similar to benzenebonds similar to benzene Bases stack verticallyBases stack vertically

Ribose in RNA; deoxyribose in DNARibose in RNA; deoxyribose in DNA (d)(d)Base-sugar = Base-sugar = (d)(d)nucleosidenucleoside

(d)(d)Base-sugar-POBase-sugar-PO44== = = (d)(d)nucleotidenucleotide

Base-pairsBase-pairs A A = = T or T T or T = = A AA A==U or UU or U==A A

C C G or G G or G CC

A C G U are in RNAA C G U are in RNA dA dC dG dT are in DNAdA dC dG dT are in DNA

D + OD + O2 2 D + OD + O2 2

Fig. 28.2 Names of purine and pyrimidines.Fig. 28.2 Names of purine and pyrimidines.Fig. 28.2 Names of purine and pyrimidines.Fig. 28.2 Names of purine and pyrimidines.

©Copyright 1999-2004 by Gene C. Lavers, Ph.D.

4

Metabolic RolesMetabolic Roles Nucleic Acid Nucleic Acid MetabolismMetabolismNucleotides IntroductionIntroduction

Metabolic RolesMetabolic Roles Nucleic Acid Nucleic Acid MetabolismMetabolismNucleotides IntroductionIntroduction

DNA and RNA Synthesis DNA and RNA Synthesis dNTP, NTPdNTP, NTP

Protein Synthesis Protein Synthesis ATP, GTPATP, GTP

Glycogen Synthesis Glycogen Synthesis UDP-glucoseUDP-glucose

Oxidative Phosphorylation Oxidative Phosphorylation ADP/ATPADP/ATP

Signal Transduction Signal Transduction cAMP cGMPcAMP cGMP

Muscle Contraction Muscle Contraction ATPATP

Electrolyte Balance Electrolyte Balance ATPATP

CoenzymesCoenzymes NAD FAD CoANAD FAD CoA

Allosteric regulatorsAllosteric regulators ATP, AMP … ATP, AMP …

DNA and RNA Synthesis DNA and RNA Synthesis dNTP, NTPdNTP, NTP

Protein Synthesis Protein Synthesis ATP, GTPATP, GTP

Glycogen Synthesis Glycogen Synthesis UDP-glucoseUDP-glucose

Oxidative Phosphorylation Oxidative Phosphorylation ADP/ATPADP/ATP

Signal Transduction Signal Transduction cAMP cGMPcAMP cGMP

Muscle Contraction Muscle Contraction ATPATP

Electrolyte Balance Electrolyte Balance ATPATP

CoenzymesCoenzymes NAD FAD CoANAD FAD CoA

Allosteric regulatorsAllosteric regulators ATP, AMP … ATP, AMP …

©Copyright 1999-2004 by Gene C. Lavers, Ph.D.

5

PRPP used in other RxPRPP used in other Rx

1.1. 1PR1PRPP + NHPP + NH22 PR PRNHNH22

2.2. Amide with gly; ATP usedAmide with gly; ATP used

3.3. 1-carbon (C1-carbon (C88) N) N1010-THFA-THFA

4.4. Gln Gln amidine (N amidine (N33))

5.5. Ring-closure – HRing-closure – H22OO

6.6. COCO22 (C (C66))

7.7. Asp (NAsp (N11) [i.e., urea cycle]) [i.e., urea cycle]

8.8. fumaratefumarate

9.9. 1-carbon (C1-carbon (C22) N) N1010-THFA-THFA

10.10. Ring-closure – HRing-closure – H22O O

PRPP used in other RxPRPP used in other Rx

1.1. 1PR1PRPP + NHPP + NH22 PR PRNHNH22

2.2. Amide with gly; ATP usedAmide with gly; ATP used

3.3. 1-carbon (C1-carbon (C88) N) N1010-THFA-THFA

4.4. Gln Gln amidine (N amidine (N33))

5.5. Ring-closure – HRing-closure – H22OO

6.6. COCO22 (C (C66))

7.7. Asp (NAsp (N11) [i.e., urea cycle]) [i.e., urea cycle]

8.8. fumaratefumarate

9.9. 1-carbon (C1-carbon (C22) N) N1010-THFA-THFA

10.10. Ring-closure – HRing-closure – H22O O

Purine synthesis Purine synthesis Nucleic Acid Nucleic Acid MetabolismMetabolism Ten steps ( 5 + 5) Ten steps ( 5 + 5) IMP IMP CytoplasmCytoplasm

Purine synthesis Purine synthesis Nucleic Acid Nucleic Acid MetabolismMetabolism Ten steps ( 5 + 5) Ten steps ( 5 + 5) IMP IMP CytoplasmCytoplasm

Fig. 28.3 Metabolic pathway forFig. 28.3 Metabolic pathway for synthesis of purinessynthesis of purinesFig. 28.3 Metabolic pathway forFig. 28.3 Metabolic pathway for synthesis of purinessynthesis of purines

©Copyright 1999-2004 by Gene C. Lavers, Ph.D.

6

IMP IMP AMP and GMP AMP and GMP Nucleic Acid Nucleic Acid MetabolismMetabolism Branched pathway Branched pathway CytoplasmCytoplasm

IMP IMP AMP and GMP AMP and GMP Nucleic Acid Nucleic Acid MetabolismMetabolism Branched pathway Branched pathway CytoplasmCytoplasm

IMP common precursor for AMP and GMPIMP common precursor for AMP and GMP AMPAMP

– GTP (GDP) cross-substrate for AMP synthesisGTP (GDP) cross-substrate for AMP synthesis

– Adenylosuccinate similar to urea cycle compoundAdenylosuccinate similar to urea cycle compound fumarate + AMPfumarate + AMP

GMPGMP– Oxidation (NADOxidation (NAD++) yields xanthine-5’P (XMP)) yields xanthine-5’P (XMP)

– ATP (AMP + PPATP (AMP + PP2Pi) amination (gln) amide yields 2Pi) amination (gln) amide yields GMPGMP

Energy costEnergy cost– IMP synthesis costs 4 ATPIMP synthesis costs 4 ATP

– AMP synthesis costs GTP (or 5 high energy bonds)AMP synthesis costs GTP (or 5 high energy bonds)

– GMP synthesis costs ATP (or 6 high energy bonds)GMP synthesis costs ATP (or 6 high energy bonds) Purine synthesis is proportional: A > GPurine synthesis is proportional: A > G PhosphorylationsPhosphorylations

– AMP AMP ADP ADP ATP ATP

– GMP GMP GDP GDP GTP GTP

IMP common precursor for AMP and GMPIMP common precursor for AMP and GMP AMPAMP

– GTP (GDP) cross-substrate for AMP synthesisGTP (GDP) cross-substrate for AMP synthesis

– Adenylosuccinate similar to urea cycle compoundAdenylosuccinate similar to urea cycle compound fumarate + AMPfumarate + AMP

GMPGMP– Oxidation (NADOxidation (NAD++) yields xanthine-5’P (XMP)) yields xanthine-5’P (XMP)

– ATP (AMP + PPATP (AMP + PP2Pi) amination (gln) amide yields 2Pi) amination (gln) amide yields GMPGMP

Energy costEnergy cost– IMP synthesis costs 4 ATPIMP synthesis costs 4 ATP

– AMP synthesis costs GTP (or 5 high energy bonds)AMP synthesis costs GTP (or 5 high energy bonds)

– GMP synthesis costs ATP (or 6 high energy bonds)GMP synthesis costs ATP (or 6 high energy bonds) Purine synthesis is proportional: A > GPurine synthesis is proportional: A > G PhosphorylationsPhosphorylations

– AMP AMP ADP ADP ATP ATP

– GMP GMP GDP GDP GTP GTP

D + OD + O2 2 D + OD + O2 2

Fig. 28.4 Conversion of IMP to AMP and GMP.Fig. 28.4 Conversion of IMP to AMP and GMP.Fig. 28.4 Conversion of IMP to AMP and GMP.Fig. 28.4 Conversion of IMP to AMP and GMP.

©Copyright 1999-2004 by Gene C. Lavers, Ph.D.

7

Purine synthesis Purine synthesis Nucleic Acid Nucleic Acid MetabolismMetabolism Control and Salvage of IMP, AMP and GMP Salvage of IMP, AMP and GMP CytoplasmCytoplasm

Purine synthesis Purine synthesis Nucleic Acid Nucleic Acid MetabolismMetabolism Control and Salvage of IMP, AMP and GMP Salvage of IMP, AMP and GMP CytoplasmCytoplasm

Control of Purine SynthesisControl of Purine Synthesis Product inhibition by AMP and GMP from IMPProduct inhibition by AMP and GMP from IMP Cross-nucletide co-substrates required Cross-nucletide co-substrates required balanced synthesis balanced synthesis Allosteric feedback inhibition of Allosteric feedback inhibition of PRPP-Gln amidotransferasePRPP-Gln amidotransferase

Salvage of free basesSalvage of free bases Nucleosides and nucleotides spontaneously hydrolyze N-Nucleosides and nucleotides spontaneously hydrolyze N--glycosidic bond -glycosidic bond

free base released free base released catabolized to urate catabolized to urate De novoDe novo synthesis of purines minimized by 1-step conversion back to synthesis of purines minimized by 1-step conversion back to

nucleoside-5’Pnucleoside-5’P– Adenine + PRPP Adenine + PRPP AMP via AMP via A-PRTaseA-PRTase– Hypoxanthine + PRPP Hypoxanthine + PRPP IMP via IMP via H-PRTaseH-PRTase– Guanine + PRPP Guanine + PRPP GMP GMP H-PRTaseH-PRTase

Gout and Lesch-Nyhan syndromesGout and Lesch-Nyhan syndromes Salvage enzymes deficient (0.1% in brain gives Lesch-Nyhan psychiatric Salvage enzymes deficient (0.1% in brain gives Lesch-Nyhan psychiatric

behavior)behavior)– Up to 5-fold extra Up to 5-fold extra de novode novo synthesis leads to excessive accumulation of urate. synthesis leads to excessive accumulation of urate.– Urate is sparingly soluble; needle crystals form in joints and kidneys Urate is sparingly soluble; needle crystals form in joints and kidneys gouty arthritis gouty arthritis

and kidney damage. Untreated L-N children die in teenage years – renal damage and kidney damage. Untreated L-N children die in teenage years – renal damage failure.failure.

Treatment: inhibition (Treatment: inhibition (XX) of ) of XOXO by allopurinol prevents excessive purine base by allopurinol prevents excessive purine base catabolism to urate, i.e., ade catabolism to urate, i.e., ade hyp hyp ——XX xan xan ——XX urate (Fig 28.5), thereby urate (Fig 28.5), thereby limiting excessive purine synthesis that occurs in untreated patientslimiting excessive purine synthesis that occurs in untreated patients

Control of Purine SynthesisControl of Purine Synthesis Product inhibition by AMP and GMP from IMPProduct inhibition by AMP and GMP from IMP Cross-nucletide co-substrates required Cross-nucletide co-substrates required balanced synthesis balanced synthesis Allosteric feedback inhibition of Allosteric feedback inhibition of PRPP-Gln amidotransferasePRPP-Gln amidotransferase

Salvage of free basesSalvage of free bases Nucleosides and nucleotides spontaneously hydrolyze N-Nucleosides and nucleotides spontaneously hydrolyze N--glycosidic bond -glycosidic bond

free base released free base released catabolized to urate catabolized to urate De novoDe novo synthesis of purines minimized by 1-step conversion back to synthesis of purines minimized by 1-step conversion back to

nucleoside-5’Pnucleoside-5’P– Adenine + PRPP Adenine + PRPP AMP via AMP via A-PRTaseA-PRTase– Hypoxanthine + PRPP Hypoxanthine + PRPP IMP via IMP via H-PRTaseH-PRTase– Guanine + PRPP Guanine + PRPP GMP GMP H-PRTaseH-PRTase

Gout and Lesch-Nyhan syndromesGout and Lesch-Nyhan syndromes Salvage enzymes deficient (0.1% in brain gives Lesch-Nyhan psychiatric Salvage enzymes deficient (0.1% in brain gives Lesch-Nyhan psychiatric

behavior)behavior)– Up to 5-fold extra Up to 5-fold extra de novode novo synthesis leads to excessive accumulation of urate. synthesis leads to excessive accumulation of urate.– Urate is sparingly soluble; needle crystals form in joints and kidneys Urate is sparingly soluble; needle crystals form in joints and kidneys gouty arthritis gouty arthritis

and kidney damage. Untreated L-N children die in teenage years – renal damage and kidney damage. Untreated L-N children die in teenage years – renal damage failure.failure.

Treatment: inhibition (Treatment: inhibition (XX) of ) of XOXO by allopurinol prevents excessive purine base by allopurinol prevents excessive purine base catabolism to urate, i.e., ade catabolism to urate, i.e., ade hyp hyp ——XX xan xan ——XX urate (Fig 28.5), thereby urate (Fig 28.5), thereby limiting excessive purine synthesis that occurs in untreated patientslimiting excessive purine synthesis that occurs in untreated patients

©Copyright 1999-2004 by Gene C. Lavers, Ph.D.

8

AzaserineAzaserine Purine Nucleotide Purine Nucleotide BiosynthesisBiosynthesis Diazo-containing AntibioticsDiazo-containing Antibiotics ClinicalClinical

AzaserineAzaserine Purine Nucleotide Purine Nucleotide BiosynthesisBiosynthesis Diazo-containing AntibioticsDiazo-containing Antibiotics ClinicalClinical

1. Glutamine analogs as affinity labels.1. Glutamine analogs as affinity labels. AzaserineAzaserine and and 6-diazo-5-oxo-norleucine6-diazo-5-oxo-norleucine

2. Diazo-containing antibiotics bind in active site of 2. Diazo-containing antibiotics bind in active site of amidotransferase. Diazo group alkylation of nucleophilic amidotransferase. Diazo group alkylation of nucleophilic cysteine residue in enzyme’s active site.cysteine residue in enzyme’s active site.

3. Expect many enzymes with Gln as substrate would be 3. Expect many enzymes with Gln as substrate would be inactivated by diazo-containing antibiotics. inactivated by diazo-containing antibiotics.

1. Glutamine analogs as affinity labels.1. Glutamine analogs as affinity labels. AzaserineAzaserine and and 6-diazo-5-oxo-norleucine6-diazo-5-oxo-norleucine

2. Diazo-containing antibiotics bind in active site of 2. Diazo-containing antibiotics bind in active site of amidotransferase. Diazo group alkylation of nucleophilic amidotransferase. Diazo group alkylation of nucleophilic cysteine residue in enzyme’s active site.cysteine residue in enzyme’s active site.

3. Expect many enzymes with Gln as substrate would be 3. Expect many enzymes with Gln as substrate would be inactivated by diazo-containing antibiotics. inactivated by diazo-containing antibiotics.

OOOO

OHOHOHOH

OOOO

HH22NNHH22NN

NHNH22

OOOO

OHOHOHOH

OOOO

N=N=CN=N=C HHN=N=CN=N=C HH

NHNH22NHNH22

OOOO

OOOO

OHOHOHOH

OOOO

N=N=CN=N=C HHN=N=CN=N=C HH

NHNH22

glutamineglutamineglutamineglutamine azaserineazaserineazaserineazaserine 6-diazo-5-oxo-norleucine6-diazo-5-oxo-norleucine6-diazo-5-oxo-norleucine6-diazo-5-oxo-norleucine

©Copyright 1999-2004 by Gene C. Lavers, Ph.D.

9

Catabolism of Purines Catabolism of Purines Nucleic Acid Nucleic Acid MetabolismMetabolism Allopurinol treatment of gout and Lesch-Nyhan syndromesAllopurinol treatment of gout and Lesch-Nyhan syndromes

Catabolism of Purines Catabolism of Purines Nucleic Acid Nucleic Acid MetabolismMetabolism Allopurinol treatment of gout and Lesch-Nyhan syndromesAllopurinol treatment of gout and Lesch-Nyhan syndromes

Fig. 28.5 Inhibition of xanthine oxidase (XO) Fig. 28.5 Inhibition of xanthine oxidase (XO) by by alloxanthine is the mechanism involved alloxanthine is the mechanism involved in in allopurinol treatment of gout and allopurinol treatment of gout and Lesch-Lesch- Nyhan syndromes.Nyhan syndromes.

Fig. 28.5 Inhibition of xanthine oxidase (XO) Fig. 28.5 Inhibition of xanthine oxidase (XO) by by alloxanthine is the mechanism involved alloxanthine is the mechanism involved in in allopurinol treatment of gout and allopurinol treatment of gout and Lesch-Lesch- Nyhan syndromes.Nyhan syndromes.

©Copyright 1999-2004 by Gene C. Lavers, Ph.D.

10

Pyrimidine Synthesis Pyrimidine Synthesis Nucleic Acid Nucleic Acid MetabolismMetabolism Multifunctional enzymes, CAD and UMP synthaseMultifunctional enzymes, CAD and UMP synthase

Pyrimidine Synthesis Pyrimidine Synthesis Nucleic Acid Nucleic Acid MetabolismMetabolism Multifunctional enzymes, CAD and UMP synthaseMultifunctional enzymes, CAD and UMP synthase

CP made by carbamoyl phosphate synthetaseCP made by carbamoyl phosphate synthetase

different from different from CPSCPS that makes CP in urea that makes CP in urea

cycle.cycle. In prokaryotes individual enzymesIn prokaryotes individual enzymes In eukaryotes 3 + 2 multifunctional enzymesIn eukaryotes 3 + 2 multifunctional enzymes

Dihydroorotate dehydrogenaseDihydroorotate dehydrogenase linked to ETS linked to ETS

via ubiquinone via ubiquinone 2 ATP. 2 ATP. Dihydroorotate oxidized to orotate by Dihydroorotate oxidized to orotate by

mitochondrial enzyme.mitochondrial enzyme. PPRP + orotate PPRP + orotate orotate nucleotide orotate nucleotide UMP + UMP +

COCO22

UMP UMP UDP UDP UTP (gln) UTP (gln) CTP CTP

CP made by carbamoyl phosphate synthetaseCP made by carbamoyl phosphate synthetase

different from different from CPSCPS that makes CP in urea that makes CP in urea

cycle.cycle. In prokaryotes individual enzymesIn prokaryotes individual enzymes In eukaryotes 3 + 2 multifunctional enzymesIn eukaryotes 3 + 2 multifunctional enzymes

Dihydroorotate dehydrogenaseDihydroorotate dehydrogenase linked to ETS linked to ETS

via ubiquinone via ubiquinone 2 ATP. 2 ATP. Dihydroorotate oxidized to orotate by Dihydroorotate oxidized to orotate by

mitochondrial enzyme.mitochondrial enzyme. PPRP + orotate PPRP + orotate orotate nucleotide orotate nucleotide UMP + UMP +

COCO22

UMP UMP UDP UDP UTP (gln) UTP (gln) CTP CTP

Fig. 28.6 Metabolic pathway for the Fig. 28.6 Metabolic pathway for the synthesis of synthesis of pyrimidines. pyrimidines.Fig. 28.6 Metabolic pathway for the Fig. 28.6 Metabolic pathway for the synthesis of synthesis of pyrimidines. pyrimidines.

©Copyright 1999-2004 by Gene C. Lavers, Ph.D.

11

Biosynthesis of CTP and TTP Biosynthesis of CTP and TTP Nucleic Acid Nucleic Acid MetabolismMetabolism THFA vs. DHFA and chemotherapyTHFA vs. DHFA and chemotherapy CytosolCytosol

Biosynthesis of CTP and TTP Biosynthesis of CTP and TTP Nucleic Acid Nucleic Acid MetabolismMetabolism THFA vs. DHFA and chemotherapyTHFA vs. DHFA and chemotherapy CytosolCytosol

Fig. 28.7 Synthesis Fig. 28.7 Synthesis of pyrimidine of pyrimidine triphosphates.triphosphates.

Inhibited at the Inhibited at the indicated sites by indicated sites by

• fluorodeoxyuridylate fluorodeoxyuridylate (FdUMP) (FdUMP)

• methotrexatemethotrexate• aminopterin aminopterin • trimethoprimtrimethoprim

Fig. 28.7 Synthesis Fig. 28.7 Synthesis of pyrimidine of pyrimidine triphosphates.triphosphates.

Inhibited at the Inhibited at the indicated sites by indicated sites by

• fluorodeoxyuridylate fluorodeoxyuridylate (FdUMP) (FdUMP)

• methotrexatemethotrexate• aminopterin aminopterin • trimethoprimtrimethoprim

©Copyright 1999-2004 by Gene C. Lavers, Ph.D.

12

Ribose to DeoxyriboseRibose to Deoxyribose Nucleic Acid Nucleic Acid MetabolismMetabolismRibonucleotide reductaseRibonucleotide reductase CytoplasmCytoplasm

Ribose to DeoxyriboseRibose to Deoxyribose Nucleic Acid Nucleic Acid MetabolismMetabolismRibonucleotide reductaseRibonucleotide reductase CytoplasmCytoplasm

OOOO

OHOHOHOH HHHH

PPPPOOPPPPOOBaseBaseBaseBase

22OOOO

OHOHOHOH OHOHOHOH

PPPPOOPPPPOOBaseBaseBaseBase

22

HH++ + + NADPNADPHHHH++ + + NADPNADPHH NADPNADP++NADPNADP++

Glutathione reductaseGlutathione reductaseGlutathione reductaseGlutathione reductase

GlutathioneGlutathioneGlutathioneGlutathione

GlutaredoxinGlutaredoxinGlutaredoxinGlutaredoxin

Ribonucleotide reductaseRibonucleotide reductaseRibonucleotide reductaseRibonucleotide reductase

FADFADFADFAD FADFADHH22FADFADHH22

Thioredoxin reductaseThioredoxin reductaseThioredoxin reductaseThioredoxin reductase

ThioredoxinThioredoxinThioredoxinThioredoxin

©Copyright 1999-2004 by Gene C. Lavers, Ph.D.

13

Uracil to Thymine: 1-carbon fragment on folate Uracil to Thymine: 1-carbon fragment on folate Deoxy Deoxy Nucleic Acids Nucleic Acids Dihydrofolate: dead-end metabolite Dihydrofolate: dead-end metabolite EnzymologyEnzymology

Uracil to Thymine: 1-carbon fragment on folate Uracil to Thymine: 1-carbon fragment on folate Deoxy Deoxy Nucleic Acids Nucleic Acids Dihydrofolate: dead-end metabolite Dihydrofolate: dead-end metabolite EnzymologyEnzymology

dUMPdUMPdUMPdUMP dTMdTMPP

dTMdTMPP

TMP synthaseTMP synthaseTMP synthaseTMP synthase

NN55,N,N1010--CHCH22-FH-FH44NN55,N,N1010--CHCH22-FH-FH44

FHFH22FHFH22

FHFH44FHFH44

NADPNADPHH + + H+H+NADPNADPHH + + H+H+

NADPNADP++NADPNADP++

Glc6PGlc6P

Pentose Pentose ShuntShunt

Pentose Pentose ShuntShunt

Rib5PRib5P

serineserineserineserine

glycineglycineglycineglycine3. Serine Serine hydroxymethhydroxymethyl yl transferasetransferase

3. Serine Serine hydroxymethhydroxymethyl yl transferasetransferase

cytoplasmcytoplasmcytoplasmcytoplasm

1111

2. Dihydrofolate2. Dihydrofolatereductasereductase2. Dihydrofolate2. Dihydrofolatereductasereductase

Fudr (fluorodeoxyuridate)Fudr (fluorodeoxyuridate)

aminopterinaminopterinmethotrexatemethotrexate(amethopterin)(amethopterin)

aminopterinaminopterinmethotrexatemethotrexate(amethopterin)(amethopterin)

Suicide inhibitorSuicide inhibitorSuicide inhibitorSuicide inhibitor

©Copyright 1999-2004 by Gene C. Lavers, Ph.D.

14

DHFA ReductaseDHFA Reductase Deoxy Nucleic Deoxy Nucleic AcidsAcidsChemotherapyChemotherapy EnzymologyEnzymology

DHFA ReductaseDHFA Reductase Deoxy Nucleic Deoxy Nucleic AcidsAcidsChemotherapyChemotherapy EnzymologyEnzymology

cytoplasmcytoplasmcytoplasmcytoplasm

NN55NN1010methyleneTHFAmethyleneTHFANN55NN1010methyleneTHFAmethyleneTHFA

NNNN

NNNN NNNN

HH22NNHH22NN NNNN

NNNNHOHOHOHO

5555

10101010

HHHH

HHHH

HH22CCHH22CC

OOOO

((GluGlu))nn((GluGlu))nn

HHHH

NNNN

NNNN NNNN

HH22NNHH22NN NNNN

NNNNHOHOHOHO

5555

10101010

HHHH

OOOO

(Glu)(Glu)(Glu)(Glu)

DHFADHFADHFADHFADihydrofolateDihydrofolateDihydrofolateDihydrofolate

Thymidylate synthaseThymidylate synthaseThymidylate synthaseThymidylate synthase

dUMPdUMPdUMPdUMP dTMPdTMPdTMPdTMP

R = H, aminopterinR = H, aminopterinR = H, aminopterinR = H, aminopterinR = CHR = CH33, methotrexate, methotrexateR = CHR = CH33, methotrexate, methotrexate

trimethoprimtrimethoprim

HNHNHNHN

HH22NNHH22NN NNNN

NHNH22NHNH22

OCHOCH33OCHOCH33

OCHOCH33OCHOCH33

OCHOCH33OCHOCH33NNNN

NNNN NNNN

HH22NNHH22NN NNNN

NNNNNHNH22NHNH22

5555

10101010

HHHH

RRRR ((gluglu))nn((gluglu))nn

©Copyright 1999-2004 by Gene C. Lavers, Ph.D.

15

Deoxyribose and ThymineDeoxyribose and Thymine Nucleic Acid Nucleic Acid MetabolismMetabolism

OverviewOverview

Deoxyribose and ThymineDeoxyribose and Thymine Nucleic Acid Nucleic Acid MetabolismMetabolism

OverviewOverview

cytoplasmcytoplasm cytoplasmcytoplasm

NMPNMPNMPNMP

NDPNDPNDPNDP

NTPNTPNTPNTP

RibonucleosideRibonucleoside bisphosphatebisphosphate

reductasereductase

RibonucleosideRibonucleoside bisphosphatebisphosphate

reductasereductasedNDPdNDP dNTPdNTP

riboseriboseriboseribose deoxyribosedeoxyribose

dATPdATP

dCTPdCTP

dGTPdGTP

dUTPdUTPdUTPdUTPdUMPdUMP

1111

22

dTMPdTMP

TMP TMP synthasesynthase

TMP TMP synthasesynthase

dTTPdTTP

pppppppp

DNADNADNADNA

DNADNADNADNA

DNADNADNADNA

DNADNADNADNA

©Copyright 1999-2004 by Gene C. Lavers, Ph.D.

16

Synthesis, Synthesis, Catabolism,Catabolism, SalvageSalvage Pyrimidine Pyrimidine Metabolism Metabolism OverviewOverview

Synthesis, Synthesis, Catabolism,Catabolism, SalvageSalvage Pyrimidine Pyrimidine Metabolism Metabolism OverviewOverview

““OMP”OMP”““OMP”OMP”

UraUraUraUra

OrotateOrotateOrotateOrotate

UMPUMPUMPUMP

ThyThyThyThy

3 steps3 steps3 steps3 steps

PRPPPRPPC.P.C.P.C.P.C.P. AspAspAspAsp

CTPCTPCTPCTP

2 Pi

1 enzyme1 enzyme1 enzyme1 enzyme

COCO22

UTPUTPUTPUTP

UDPUDPUDPUDP dUDPdUDPdUDPdUDP dUMPdUMPdUMPdUMP dTMPdTMPdTMPdTMP

RNARNA

-Ala-Ala-Ala-Ala 2-MeBu2-MeBu2-MeBu2-MeBu

CytCytCytCyt

??

dTTPdTTPdTTPdTTP

PPi

GlycogenGlycogen

DNA

DNA

UrdUrdUrdUrd ThdThdThdThdCydCydCydCyd

©Copyright 1999-2004 by Gene C. Lavers, Ph.D.

17

Biosynthesis and Degradation Biosynthesis and Degradation

of Nucleotidesof Nucleotides

Biosynthesis and Degradation Biosynthesis and Degradation

of Nucleotidesof Nucleotides

ENDENDENDEND