2. The nucleic acid metabolism disorders of
purine and pyrimidine.
Hyperuricemia, orotacidurie, therapy.
1
Sugar - base linkage
Nucleoside
RNA: adenosine, guanosine, cytidine, & uridine
DNA: deoxyadenosine, deoxyguanosine, deoxycytidine, & thymidine
Base above plane of
sugar, linkage is 
2
Purines & Pyrimidines
Note: ring atom #s RNA DNA
3
Nucleotides: monomeric units of nucleic acids
5’ nucleotide - most common 3’ nucleotide
Adenosine 5’-triphosphate
Deoxyguanosine
3’ monophosphate
Nucleotide: nucleoside joined to one or more phosphate groups
by an ester linkage 4
Backbone of DNA & RNA
3’-to-5’ phosphodiester linkages
Sugar, red. Phosphate, blue 5
TEST
6
7
Biosynthesis of purine and pyrimidine nucleotides
• all cells needs ribonucleosides, deoxyribonucleosides and
their phosphates
• not esencial (2 biosynthetic pathways)
• purine and pyrimidine basis from food are not used for biosynthesis,
cleved for catabolism (pancreatic endonucleases)
• biosynthesis purine and pyrimidine basis (2 pathways):
•1. de novo 2. salvage pathway
• location :- liver
• needs: sugar (PPRP), AA(glycine, glutamine, aspartate),
. coenzyme: tetrahydrofolate
• synthesis of purine and pyrimidine nucleotides are coordinated
7
TEST
Precursore molecules for purine and
pyrimidine nucleotides
• 3 main compounds:
• 1) tetrahydrofolate
• 2) glutamine
• 3) PRPP – 5-phosphoribosyl-1-pyrophosphate
N
N
OH
NH2N
CO NH CH
CH2
CH2
COO-
COO-
H
CH2 N
N
H
H
CH COO
NH3
(CH2)2C -
+
O
NH2
O
O
CH2OP
O
O
O-
OH
OH
P P
O
OO
O
-- O
O
-
8
9
Importance of folic acid for biosynthesis of
NA bases
Folate
Green leafy vegetables,
liver, whole grains, yeast, k
N
N
O H
N
N
C H2 N
H2 N
C O N H C H
C H2
C H2
C O O C
O O -
H
Used form in human is tetrahydrofolate
tetrahydrofolate
9
10
(dihydro)folatereduktase
folate
N
N
OH
NH2N
CO NH CH
CH2
CH2
COO-
COO-
H
CH2 N
N
H
H
tetrahydrofolate
dihydrofolate
NADPH + H+
NADP
NADP
NADPH + H+
N
N
OH
NH2N
CO NH CH
CH2
CH2
COO-
COO-
H
CH2 N
N
H
Formation of
tetrahydrofolate
+
+
DEHYDOGENATION
10
11
Methotrexate (anticancer agent)
Inhibitors (dihydro)folatereductase:
NH2
H2N
CH2 N
CH3
C NH
O
C
COO-
H
CH2
CH2
COO-
N
N
Trimethoprim (bacteriostaticum)
N
N
NH2
H2N
OCH3
OCH3
OCH3 11
12
Dihydrofolate reductase - an objective antitumor
therapy.
Dihydrofolate reductase was the first enzyme for which focused antitumor
therapy.
The first-used inhibitor was aminopterin.
It binds to the enzyme 1000 times tighter than folate, acts as a competitive
inhibitor.
Currently used methotrexate and similar derivatives.
All drugs which affect the synthesis of purines and pyrimidines, deplete
rapidly dividing cells - but not only cancer cells but also cells in the bone
marrow and GI tract cells such as hair follicles.
12
13
N
N
OH
NH2N
CO NH CH
CH2
CH2
COO-
COOCH2
N
N
H
CH2
N-5,N-10- methylen H4F – synthesis of thymin
N
N
OH
NH2N
CO NH CH
CH2
CH2
COO-
COOCH2
N
N
H
CHOH
N-10-formyl H4F – synthesis of purins
5 10
1
3
Using of tetrahydrofolate
13
Importance of glutamin for purine and
pyrimidine biosynthesis
CH COO
NH3
(CH2)2C -
+
O
NH2
- Donor of aminogroup
Glutamine antagonists inhibits synthesis of purines and
pyrimidines
CH2 CH
NH2
COOHOC
O
CH
N
N
azaserin 14
15
Necessary for synthesis:
Purine nucleotides
Pyrimidine nucleotides
NAD+, NADP+
PRPP - phosphoribosylphyridoxalphosphate
O
O
CH2OP
O
O
O-
OH
OH
P P
O
OO
O
-- O
O
-
15
Ribosa-5P + ATP  PRPP + AMP
PRPP-synthetase
Synthesis of PRPP
O
O
CH2OP
O
O
O-
OH
OH
P P
O
OO
O
-- O
O
-
ribose-5-phosphate
(pentose cycle),
activeted penthose
16
17
TEST
18
19
Differences in purine and pyrimidine synthesis
Purins
First PRPP…
Pyrimidins
First heterocycle ribose-P from
PRPP
O
O
CH2OP
O
O
O-
OH
OH
P P
O
OO
O
-- O
O
-
N
NO
O
COO
-
H
Synthesis - puzzle – one part to others.
Diffrence in the beginning :
–purines : first PRPP and than is form base
- Pyrimidines : first base and than ribosa-5-P from PRPP.
19
20
1) BIOSYNTESIS of PYRIMIDINS
N
O
H
O
12
3
4
5
6
N
Ribosa-P
glutamin
HCO3
•2.
aspartate
• 3. PRPP
COO-
Orotidinmono-P
Decarboxylation – uridin mono-P
Origin of atoms in pyrimidines
 karbamoyl-P•1.
TEST
20
21
CYTOPLASM
• 1 Glutamine + 2 ATP + HCO3

karbamoyl-P + glutamate + 2 ADP + Pi
• syntesis of karbamoyl -P
CO
NH2
O P
O
O
O-
Karbamoyl-P-synthetase
-energy, enzym karbamoylphosphatesynthetase II
Inhibition by UTP („inhibition by product“) and
aktivation by ATP.
BIOSYNTESIS OF PYRIMIDINS
21
22
H2N
CH
CH2
COO
COO
-
-
H2N
C O
P OO
O
-
-
Pi
C
N
CH
CH2
COOO
COO
NH2
H
-
H2
O
-
HN
C
N
CH
CH2
C
O
COO
O
-
H
HN
C
N
C
O
COO
O
-
H
O
O P
O
O
CH2
OP
O
O
O
O P
O
O
O
-
--
-
--
-
HN
C
N
C
O
COO
O
-
O
O
O
P O CH2
O
-
-
HN
C
N
C
O
O
O
O
O
P O CH2
O
CO2
karbamoylaspartate
dihydroorotate
orotate
Orotidinmono-P PRPP
Uridinmono-P
(UMP)
karbamoylP
aspartate
BIOSYNTESIS OF PYRIMIDINS
22
23
ATP
Biosyntesis of UTP and CTP
UMP
UDP 
ADP
ATP
ADP + P
glutamine
glutamate
CTP
ATP
ADP
UTP Uridin tri-P
cytidin tri-P
BIOSYNTESIS OF PYRIMIDINS
23
24
dTMP (methylation)
Methylation- H4F
N
N
O
O
CH3
CH2
OH
O
H
Methylen group in H4F is reduced to methyl dUMP
Deoxythymidintri-P
24
25
UDP  dUDP  dUMP TMP
Thymidylatesynthase
(enzym dependent on folate)
Dihydrofolatereductase
Synthesis of TMP
Methylen –H4F H2F
serin
H4F
glycin
NADPH
NADP
Transport of methylene (
H4F …. H2F)
Anticancer drugs 25
26
N
N
OH
NH2N
CO NH CH
CH2
CH2
COO-
COOCH2
N
N
H
CH2
N
N
OH
NH2N
CO NH CH
CH2
CH2
COO-
COOCH2
NH
N
N
N
OH
NH2N
CO NH CH
CH2
CH2
COO-
COO-
H
CH2 N
N
H
H
NADPH + H+
NADP+
CH2
CH2-H4F
H2F
H4F
H
H
H
H
26
27
thymidylate synthase
The administration of fluorouracil
organism conversion to
5-fluorodeoxyuridine monophosphate
Competitive inhibition
thymidylatesynthasy
The cytostatic effect of a drug
Thymidylate
synthase because it is blocked by
a competitive inhibitor, which in
effect prevents dTMP, resulting in
a slowdown (disabling) of cell
division.
27
28
2. Synthesis of pyrimidins by salvage pathway
Uracil
or
Cytosin
Ribosa-1-P
Pi
Uridin
or
Cytidin
Thymin
Deoxyribosa-1-P
Pi
Thymidin
1. nucleosides
•thymidin + ATP  TMP + ADP
•cytidin + ATP  CMP + ADP
•deoxycytidin + ATP  dCMP + ADP
•uridin + ATP  UMP + ADP
2. Kinase - phosphorylation
Salvage pathway –
extrahepatal tissues
28
29
Regulation of biosyntesis of pyrimidins
• Karbamoyl-P-synthetase:
inhibition by UTP, purins nucleotides,
activation by PRPP
 Allosteric:
 dependence on cell cycle
KarbamoylP-synthetase in S phase is more
sensitive to activation by PRPP
29
30
Degradation of pyrimidins nucleotides
deaminatio
n
reduktio
n
-alanin
-aminoisobutyrate
Pyrimidins – to the simple compounds – in urine
Pyrimidine base, we are able in our body break down into simpler components
STEPS:
a) Release of P
b) Release of sugar
c) Degradation of pyrimidine base
End products of cleavege of pyrimidines:
NH3, CO2, -alanin, ( -aminoisobutyrate)
Soluble metabolist – excretion by urine
TEST
30
Inherited metabolic disorder of pyrimidine metabolism
• Orotic aciduria (UMP synthase deficiency)
• Dihydropyriminidase deficiency
• Thymidine phosphorylase deficiency MNGIE
31
This gene encodes a uridine 5'-monophosphate synthase. The encoded
protein is a bifunctional enzyme that catalyzes the final two steps of the de
novo pyrimidine biosynthetic pathway. The first reaction is carried out by the Nterminal
enzyme orotate phosphoribosyltransferase which converts orotic
acid to orotidine-5'-monophosphate. The terminal reaction is carried out by the
C-terminal enzyme OMP decarboxylase which converts orotidine-5'monophosphate
to uridine monophosphate. Defects in this gene are the
cause of hereditary orotic aciduria.
Inherited metabolic disorder of pyrimidine metabolism
1. uridine 5'-monophosphate synthase deficiency (orotic aciduria)
TEST
32
TEST
UMP synthase
uridine 5'-monophosphate synthase
33
Inherited metabolic disorder of pyrimidine metabolism
• 2. Dihydropyriminidase deficiency
34
Dihydropyrimidinase (DHP) is the second enzyme in
the catabolism of 5-fluorouracil (5FU), and it has been suggested
that patients with a deficiency of this enzyme are at
risk from developing severe 5FU-associated toxicity.
Inherited metabolic disorder of pyrimidine metabolism
• 2. Dihydropyriminidase deficiency
35
Deficiency of the cytosolic
enzyme thymidine
phosphorylase (TP) causes
a multisystem disorder
called mitochondrial
neurogastrointestinal
encephalomyopathy
(MNGIE) syndrome.
Clinical symptoms are
gastrointestinal
dysfunction, muscle
involvement and
neurological deterioration.
Inherited metabolic disorder of pyrimidine metabolism
• 3. thymidine phosphorylase deficiency
• mitochondrial neurogastrointestinal encephalomyopathy
(MNGIE) syndrome
36
Inherited metabolic disorder of pyrimidine metabolism
• 3. thymidine phosphorylase deficiency
• mitochondrial neurogastrointestinal encephalomyopathy
(MNGIE) syndrome
37
38
Ribosa-5-P
3 glycin
HCO3
-
aspartate
formyl-H4F
glutamin
1 PRPP
formyl-H4F
2
4
6
7
8
Biosyntesis of purins
(multienzym complex)
Inosin-5-P (IMP)
5
cytoplasm
liver
N
HN
O
N
N
C
C
C
38
39
O
O P
O
O
CH2
OP
O
O
O
O P
O
O
O
-
--
-
O
CH2
OP
O
O
O NH2
-
-
O
CH2
OP
O
O
O NH
C O
CH2
NH3
-
-
O
CH2
OP
O
O
O NH
C O
CH2
NH CHO
-
-O
CH2
OP
O
O
O NH
C NH
CH2
NH CHO
-
-
N
N
O
O
O
P O CH2
O
H2N
-
-
N
N
O
O
O
P O CH2
O
H2N
OOC-
-
N
N
O
O
O
P O CH2
O
H2N
CO
H2N
-
N
N
O
O
O
P O CH2
O
NH
CO
H2N
OHC
-
O
O
O
P O CH2
O
-
N
N
O
N
N
H
H
Biosyntesis of IMP
Gln Glu
inosinmonophosphate
ATP, glycin
ADP
Formyl-
THFTHF
Glu Gln
H2O
CO2
asp
formylTHF
THF
H2O
phosphoribosylaminPRPP
Inosin-5-P (IMP)
Biosyntesis of purins
39
40
N
N
O
N
N
H
ribosa-5-P
Inosin-5-P (IMP)-Initial substance for synthesis of
other basis
aspartate, GTP
amination
AMP
oxidation aminati
on
GMP
Glutamin, ATP
XMP
xantosinmonoP
Biosyntesis of purins
40
41
N
N
O
N
N
Ribosa
H
P
N
N
N
CH CH2COO
COO
N
N
Ribosa P
-
-
N
N
NH2
N
N
Ribosa P
N
N
O
O
N
N
RibosaH P
N
N
O
H2N N
N
RibosaH P
HH
Syntesis of AMP a GM
IMP
Asp
GTP
GDP + Pi fumarate
AMP
NAD+
NADH + H+ ATP AMP + PPi
XMP GMP
Gln Glu
41
42
Inhibitors of syntesis of purins (cytostatics)
• inhibitors dihydrofolate reductase
• analogy glutamin (azaserin)
• 6-merkaptopurin- inhibition of change IMP
to AMP and GMP
N
N
SH
N
N
H
merkaptopurin
42
43
Syntesis of purins by salvage pathway
Extrahepatal tissue
Purin + PRPP  purinnukleotidmonoP + PP
phosphoribosyltransferase
Recyclation of purins
O
O
CH2OP
O
O
O-
OH
OH
P P
O
OO
O
-- O
O
-
phosphoribosyltransferase
AMP
adeninphosphoribosyltransfera
se
43
44
Syntesis of nukleotiddiP and triP
nukleosidmonoP
nukleotiddiP
nukleotidtriP
ATP
ADP
ATP
ADP
44
45
Regulation of biosyntesis of purins
• concentration of PRPP
Speed of synthesis
Speed of degradationSpeed of use
• inhibice PRPP-glutamylamidotransferase by AMP
and GMP (end products)
IMP
AMP
GMP
GMP

AMP

1.
2.
3.
45
46
ribonucleotidreductase
Nucleotiddiphosphate  deoxynucleotiddiphosphate
cofactor protein bound
46
Inherited metabolic disorder of
pyrimidine/purine metabolism
• 4. PPRP synthase superactivity
47
TEST
Inherited metabolic disorder of purine metabolism
• 1.Adenylosuccinate lyase deficiency (ADSL)
48TEST
Inherited metabolic disorder of purine metabolism
• 1. HGPRT deficiency
49
TEST
Adenine phosphoryl transferase
Inherited metabolic disorder of purine metabolism
• 2. Adenine phosphoryl transferase
• deficiency
50
TEST
51
Degradation of purines
AMP,GMP,
IMP,XMP
5-nucleotidase
guanosin, inosin,
xantosin + Pi
nukleosidphosphorylase
Adenosin + Pi,
guanin,
hypoxantin,
xantin
+ riboso-1-P
adenosindeaminase
inosinnukleosidphosphorylase
Cleavage of P
liver
51
52
Enzyme deficiency leads to the accumulation of toxic deoxyadenosine,
which affects immunocompetent cells
One of the causes of severe combined immunodeficiency (severe
combined immunodeficiency disease-SCID).
Inherited metabolic disorder of purine metabolism
• 3. adenosine deaminase deficiency
52
53
hypoxantin xantin
Uric acids
xantinoxidase
guanin
guanase
end metabolit primate,
….. (400-600 mg /den)
Inhibition by
allopurinolem
Degradation of purins
53
Xanthine Oxidase
• A homodimeric protein
• Contains electron transfer proteins
– FAD
– Mo-pterin complex in +4 or +6 state
– Two 2Fe-2S clusters
• Transfers electrons to O2  H2O2
– H2O2 is toxic
– Disproportionated to H2O and O2 by catalase
54
55
Allopurinol – competitive inhibitor of
xantinoxidase
Gout: allopurinol inhibits the oxidation of hypoxanthine to
xanthine
hypoxanthine is more soluble and more readily excreted
N
N
OH
N
N
H
55
Allopurinol (structural analog of hypoxanthine ) is
converted to the xanthine oxypurinol
(= alloxanthin ), which binds tightly to the enzyme and
prevents its further catalytic activity.
Allopurinol is the " suicide " inhibitor of xanthine oxidase ,
reduces the concentration of uric
acid in the blood and thus the other fluids ( eg . synovial )
; amount of secreted urate
decreases excretion rises somewhat better soluble
hypoxanthine and xanthine . moreover
final metabolite is not a single product but three , so
decreasing the risk of excess constants
solubility that would be the case for one of the final
product .
56
Inherited metabolic disorder of purine metabolism
• 4. Xanthinuria
• lack of enzyme, xantin oxidase
57TEST
58
59
increasing of production and decreasing of excretion of uric acid
 defect in salwa pathway
(deficit hypoxantin-guaninphosphoribosyltransferase) (HGPRT)
hypoxantin + PRPP  IMP + PP
 decrease of clearance in kidney
Keeping of crystals of UA in tissue
Inherited metabolic disorder of purine metabolism
• 5. Gout
• enzyme deficiency HGPRT
• enzyme deficiency glucose-6-phosphatase
• increased enzyme activity PRPPsynthetase
GOUT (hyperuricemia)
59
Gout
• Impaired excretion or overproduction of uric acid
• Uric acid crystals precipitate into joints (Gouty Arthritis),
kidneys, ureters (stones)
• Lead impairs uric acid excretion – lead poisoning from
pewter drinking goblets
– Fall of Roman Empire?
• Xanthine oxidase inhibitors inhibit production of uric
acid, and treat gout
• Allopurinol treatment – hypoxanthine analog that
binds to Xanthine Oxidase to decrease uric acid
production
60
61
62
63
Hyperuricemia is an abnormally high level of uric acid in the blood. In the pH
conditions of body fluid, uric acid exists largely as urate, the ion form.[1][2] The
amount of urate in the body depends on the balance between the amount of purines
eaten in food, the amount of urate synthesised within the body (e.g., through cell
turnover), and the amount of urate that is excreted in urine or through the
gastrointestinal tract.[2] In humans, the upper end of the normal range is 360 µmol/L
(6 mg/dL) for women and 400 µmol/L (6.8 mg/dL) for men.
64
6. Lesch-Nyhan Syndrome
• A defect in production or activity of
HGPRT
– Causes increased level of Hypoxanthine and Guanine (
in degradation to uric acid)
• Also,PRPP accumulates
– stimulates production of purine nucleotides (and thereby
increases their degradation)
• Causes gout-like symptoms, but also neurological symptoms 
spasticity, aggressiveness, self-mutilation
• First neuropsychiatric abnormality that was attributed to a
single enzyme
Inherited metabolic disorders of purine metabolism
65
TEST
Lesch–Nyhan syndrome (LNS),
also known as Nyhan's syndrome, Kelley-Seegmiller syndrome, and juvenile
gout,[1] is a rare inherited disorder caused by a deficiency of the enzyme
hypoxanthine-guanine phosphoribosyltransferase (HGPRT), produced
by mutations in the HPRT gene located on the X chromosome. LNS affects about
one in 380,000 live births.[2] The disorder was first recognized and clinically
characterized by medical student Michael Lesch and his mentor, pediatrician
William Nyhan, who published their findings in 1964.[3]
The HGPRT deficiency causes a build-up of uric acid in all body fluids. This results
in both hyperuricemia and hyperuricosuria, associated with severe gout and
kidney problems.
66
67
Inherited metabolic disorders of purine metabolism
d adenosine phosphoribosyltransferase 67
TEST