nucleotides synthesis and degradation l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Nucleotides: Synthesis and Degradation PowerPoint Presentation
Download Presentation
Nucleotides: Synthesis and Degradation

Loading in 2 Seconds...

play fullscreen
1 / 76

Nucleotides: Synthesis and Degradation - PowerPoint PPT Presentation


  • 733 Views
  • Uploaded on

Nucleotides: Synthesis and Degradation. Nitrogenous Bases. Planar, aromatic, and heterocyclic Derived from purine or pyrimidine Numbering of bases is “unprimed”. Nucleic Acid Bases. Pyrimidines. Purines. Sugars. Pentoses (5-C sugars) Numbering of sugars is “primed”. Sugars.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Nucleotides: Synthesis and Degradation' - Antony


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
nitrogenous bases
Nitrogenous Bases
  • Planar, aromatic, and heterocyclic
  • Derived from purine or pyrimidine
  • Numbering of bases is “unprimed”
nucleic acid bases
Nucleic Acid Bases

Pyrimidines

Purines

sugars
Sugars
  • Pentoses (5-C sugars)
  • Numbering of sugars is “primed”
sugars5
Sugars

D-Ribose and 2’-Deoxyribose

*Lacks a 2’-OH group

nucleosides
Nucleosides
  • Result from linking one of the sugars with a purine or pyrimidine base through an N-glycosidic linkage
    • Purines bond to the C1’ carbon of the sugar at their N9 atoms
    • Pyrimidines bond to the C1’ carbon of the sugar at their N1 atoms
phosphate groups
Phosphate Groups
  • Mono-, di- or triphosphates
  • Phosphates can be bonded to either C3 or C5 atoms of the sugar
nucleotides
Nucleotides
  • Result from linking one or more phosphates with a nucleoside onto the 5’ end of the molecule through esterification
nucleotides10
Nucleotides
  • RNA (ribonucleic acid) is a polymer of ribonucleotides
  • DNA (deoxyribonucleic acid) is a polymer of deoxyribonucleotides
  • Both deoxy- and ribonucleotides contain Adenine, Guanine and Cytosine
    • Ribonucleotides contain Uracil
    • Deoxyribonucleotides contain Thymine
nucleotides11
Nucleotides
  • Monomers for nucleic acid polymers
  • Nucleoside Triphosphates are important energy carriers (ATP, GTP)
  • Important components of coenzymes
    • FAD, NAD+ and Coenzyme A
naming conventions
Naming Conventions
  • Nucleosides:
    • Purine nucleosides end in “-sine”
      • Adenosine, Guanosine
    • Pyrimidine nucleosides end in “-dine”
      • Thymidine, Cytidine, Uridine
  • Nucleotides:
    • Start with the nucleoside name from above and add “mono-”, “di-”, or “triphosphate”
      • Adenosine Monophosphate, Cytidine Triphosphate, Deoxythymidine Diphosphate
in class activities
In-Class Activities
  • Look at the Nucleotide Structures
  • Take the Nucleotide Identification Quiz
  • Be prepared to identify some of these structures on an exam. Learn some “tricks” that help you to distinguish among the different structures
nucleotide metabolism
Nucleotide Metabolism
  • PURINE RIBONUCLEOTIDES: formed de novo
    • i.e., purines are not initially synthesized as free bases
    • First purine derivative formed is Inosine Mono-phosphate (IMP)
      • The purine base is hypoxanthine
      • AMP and GMP are formed from IMP
purine nucleotides
Purine Nucleotides
  • Get broken down into Uric Acid (a purine) Buchanan (mid 1900s) showed where purine ring components came from:

N1: Aspartate Amine

C2, C8: Formate

N3, N9: Glutamine

C4, C5, N7: Glycine

C6: Bicarbonate Ion

purine nucleotide synthesis at a glance
Purine Nucleotide Synthesis at a Glance
  • ATP is involved in 6 steps
  • PRPP in the first step of Purine synthesis is also a precursor for Pyrimidine Synthesis, His and Trp synthesis
    • Role of ATP in first step is unique– group transfer rather than coupling
  • In second step, C1 notation changes from a to b (anomers specifying OH positioning on C1 with respect to C4 group)
  • In step 2, PPi is hydrolyzed to 2Pi (irreversible, “committing” step)
coupling of reactions
Coupling of Reactions
  • Hydrolyzing a phosphate from ATP is relatively easy

G°’= -30.5 kJ/mol

    • If endergonic reaction released energy into cell as heat energy, wouldn’t be useful
    • Must be coupled to an exergonic reaction
  • When ATP is a reactant:
    • Part of the ATP can be transferred to an acceptor: Pi, PPi, adenyl, or adenosinyl group
    • ATP hydrolysis can drive an otherwise unfavorable reaction

(synthetase; “energase”)

purine biosynthetic pathway
Purine Biosynthetic Pathway
  • Channeling of some reactions on pathway organizes and controls processing of substrates to products in each step
    • Increases overall rate of pathway and protects intermediates from degradation
  • In animals, IMP synthesis pathway shows channeling at:
    • Reactions 3, 4, 6
    • Reactions 7, 8
    • Reactions 10, 11
in class activity
In Class Activity***

Calculate how many ATP equivalents are needed for the de novo synthesize IMP. Assume that all of the substrates (R5P, glutamine, etc) are available

Note: You should be able to do this calculation for the synthesis of

any of the nucleoside monophosphates

regulatory control of purine nucleotide biosynthesis
Regulatory Control of Purine Nucleotide Biosynthesis
  • GTP is involved in AMP synthesis and ATP is involved in GMP synthesis (reciprocal control of production)
  • PRPP is a biosynthetically “central” molecule (why?)
    • ADP/GDP levels – negative feedback on Ribose Phosphate Pyrophosphokinase
    • Amidophosphoribosyl transferase is activated by PRPP levels
    • APRT activity has negative feedback at two sites
      • ATP, ADP, AMP bound at one site
      • GTP,GDP AND GMP bound at the other site
  • Rate of AMP production increases with increasing concentrations of GTP; rate of GMP production increases with increasing concentrations of ATP
regulatory control of purine biosynthesis
Regulatory Control of Purine Biosynthesis
  • Above the level of IMP production:
    • Independent control
    • Synergistic control
    • Feedforward activation by PRPP
  • Below level of IMP production
    • Reciprocal control
  • Total amounts of purine nucleotides controlled
  • Relative amounts of ATP, GTP controlled
purine catabolism and salvage
Purine Catabolism and Salvage
  • All purine degradation leads to uric acid (but it might not stop there)
  • Ingested nucleic acids are degraded to nucleotides by pancreatic nucleases, and intestinal phosphodiesterases in the intestine
  • Group-specific nucleotidases and non-specific phosphatases degrade nucleotides into nucleosides
    • Direct absorption of nucleosides
    • Further degradation

Nucleoside + H2O  base + ribose (nucleosidase)

Nucleoside + Pi  base + r-1-phosphate (n. phosphorylase)

NOTE: MOST INGESTED NUCLEIC ACIDS ARE DEGRADED AND EXCRETED.

intracellular purine catabolism
Intracellular Purine Catabolism
  • Nucleotides broken into nucleosides by action of 5’-nucleotidase (hydrolysis reactions)
  • Purine nucleoside phosphorylase (PNP)
    • Inosine  Hypoxanthine
    • Xanthosine  Xanthine
    • Guanosine  Guanine
    • Ribose-1-phosphate splits off
      • Can be isomerized to ribose-5-phosphate
  • Adenosine is deaminated to Inosine (ADA)
intracellular purine catabolism27
Intracellular Purine Catabolism
  • Xanthine is the point of convergence for the metabolism of the purine bases
  • Xanthine  Uric acid
    • Xanthine oxidase catalyzes two reactions
  • Purine ribonucleotide degradation pathway is same for purine deoxyribonucleotides
xanthosine degradation
Xanthosine Degradation
  • Ribose sugar gets recycled (Ribose-1-Phosphate  R-5-P )
  • – can be incorporated into PRPP (efficiency)
  • Hypoxanthine is converted to Xanthine by Xanthine Oxidase
  • Guanine is converted to Xanthine by Guanine Deaminase
  • Xanthine gets converted to Uric Acid by Xanthine Oxidase
xanthine oxidase
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
the purine nucleotide cycle
THE PURINE NUCLEOTIDE CYCLE

AMP + H2O  IMP + NH4+(AMP Deaminase)

IMP + Aspartate + GTP  AMP + Fumarate + GDP + Pi(Adenylosuccinate Synthetase)

COMBINE THE TWO REACTIONS:

Aspartate + H2O + GTP  Fumarate + GDP + Pi+ NH4+

The overall result of combining reactions is deamination of Aspartate to Fumarate at the expense of a GTP

purine nucleotide cycle
Purine Nucleotide Cycle***

In-Class Question: Why is the purine nucleotide cycle important in muscle metabolism during a burst of activity?

uric acid excretion
Uric Acid Excretion
  • Humans – excreted into urine as insoluble crystals
  • Birds, terrestrial reptiles, some insects – excrete insoluble crystals in paste form
    • Excess amino N converted to uric acid
      • (conserves water)
  • Others – further modification :

Uric Acid  Allantoin  Allantoic Acid  Urea  Ammonia

purine salvage
Purine Salvage
  • Adenine phosphoribosyl transferase (APRT)

Adenine + PRPP  AMP + PPi

  • Hypoxanthine-Guanine phosphoribosyl transferase (HGPRT)

Hypoxanthine + PRPP  IMP + PPi

Guanine + PRPP  GMP + PPi

(NOTE: THESE ARE ALL REVERSIBLE REACTIONS)

AMP,IMP,GMP do not need to be resynthesized de novo !

a case study gout
A CASE STUDY : GOUT
  • A 45 YEAR OLD MAN AWOKE FROM SLEEP WITH A PAINFUL AND SWOLLEN RIGHT GREAT TOE. ON THE PREVIOUS NIGHT HE HAD EATEN A MEAL OF FRIED LIVER AND ONIONS, AFTER WHICH HE MET WITH HIS POKER GROUP AND DRANK A NUMBER OF BEERS.
  • HE SAW HIS DOCTOR THAT MORNING, “GOUTY ARTHRITIS” WAS DIAGNOSED, AND SOME TESTS WERE ORDERED. HIS SERUM URIC ACID LEVEL WAS ELEVATED AT 8.0 mg/dL (NL < 7.0 mg/dL).
  • THE MAN RECALLED THAT HIS FATHER AND HIS GRANDFATHER, BOTH OF WHOM WERE ALCOHOLICS, OFTEN COMPLAINED OF JOINT PAIN AND SWELLING IN THEIR FEET.
a case study gout36
A CASE STUDY : GOUT
  • THE DOCTOR RECOMMENDED THAT THE MAN USE NSAIDS FOR PAIN AND SWELLING, INCREASE HIS FLUID INTAKE (BUT NOT WITH ALCOHOL) AND REST AND ELEVATE HIS FOOT. HE ALSO PRESCRIBED ALLOPURINOL.
  • A FEW DAYS LATER THE CONDITION HAD RESOLVED AND ALLOPURINOL HAD BEEN STOPPED. A REPEAT URIC ACID LEVEL WAS OBTAINED (7.1 mg/dL). THE DOCTOR GAVE THE MAN SOME ADVICE REGARDING LIFE STYLE CHANGES.
slide37
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

Gout
slide41
ALLOPURINOL IS A XANTHINE OXIDASE INHIBITORA SUBSTRATE ANALOG IS CONVERTED TO AN INHIBITOR, IN THIS CASE A “SUICIDE-INHIBITOR”
slide42

ALCOHOL CONSUMPTION AND GOUT

Choi HK, Atkinson K, Karlson EW et al. . 2004. “Alcohol intake and risk of incident gout in men:

a prospective study”. Lancet 363: 1277-1281

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

Lesch-Nyhan Syndrome
purine autism
25% of autistic patients may overproduce purines

To diagnose, must test urine over 24 hours

Biochemical findings from this test disappear in adolescence

Must obtain urine specimen in infancy, but it’s difficult to do!

Pink urine due to uric acid crystals may be seen in diapers

Purine Autism
in class question
IN-CLASS QUESTION***
  • IN von GIERKE’S DISEASE, OVERPRO- DUCTION OF URIC ACID OCCURS. THIS DISEASE IS CAUSED BY A DEFICIENCY OF GLUCOSE-6-PHOSPHATASE.
    • EXPLAIN THE BIOCHEMICAL EVENTS THAT LEAD TO INCREASED URIC ACID PRODUCTION?
    • WHY DOES HYPOGLYCEMIA OCCUR IN THIS DISEASE?
    • WHY IS THE LIVER ENLARGED?
pyrimidine ribonucleotide synthesis
Pyrimidine Ribonucleotide Synthesis
  • Uridine Monophosphate (UMP) is synthesized first
    • CTP is synthesized from UMP
  • Pyrimidine ring synthesis completed first; then attached to ribose-5-phosphate

N1, C4, C5, C6 : Aspartate

C2 : HCO3-

N3 : Glutamine amide Nitrogen

ump synthesis overview
UMP Synthesis Overview
  • 2 ATPs needed: both used in first step
    • One transfers phosphate, the other is hydrolyzed to ADP and Pi
  • 2 condensation rxns: form carbamoyl aspartate and dihydroorotate (intramolecular)
  • Dihydroorotate dehydrogenase is an intra-mitochondrial enzyme; oxidizing power comes from quinone reduction
  • Attachment of base to ribose ring is catalyzed by OPRT; PRPP provides ribose-5-P
    • PPi splits off PRPP – irreversible
  • Channeling: enzymes 1, 2, and 3 on same chain; 5 and 6 on same chain
omp decarboxylase the most catalytically proficient enzyme
OMP DECARBOXYLASE : THE MOST CATALYTICALLY PROFICIENT ENZYME
  • FINAL REACTION OF PYRIMIDINE PATHWAY
  • ANOTHER MECHANISM FOR DECARBOXYLATION
  • A HIGH ENERGY CARBANION INTERMEDIATE NOT NEEDED
  • NO COFACTORS NEEDED !
  • SOME OF THE BINDING ENERGY BETWEEN OMP AND THE ACTIVE SITE IS USED TO STABILIZE THE TRANSITION STATE
    • “PREFERENTIAL TRANSITION STATE BINDING”
ump utp and ctp
UMP  UTP and CTP
  • Nucleoside monophosphate kinase catalyzes transfer of Pi to UMP to form UDP; nucleoside diphosphate kinase catalyzes transfer of Pi from ATP to UDP to form UTP
  • CTP formed from UTP via CTP Synthetase driven by ATP hydrolysis
    • Glutamine provides amide nitrogen for C4 in animals
regulatory control of pyrimidine synthesis
Regulatory Control of Pyrimidine Synthesis
  • Differs between bacteria and animals
    • Bacteria – regulation at ATCase rxn
  • Animals – regulation at carbamoyl phosphate synthetase II
    • UDP and UTP inhibit enzyme; ATP and PRPP activate it
    • UMP and CMP competitively inhibit OMP Decarboxylase

*Purine synthesis inhibited by ADP and GDP at ribose phosphate pyrophosphokinase step, controlling level of PRPP  also regulates pyrimidines

orotic aciduria
Caused by defect in protein chain with enzyme activities of last two steps of pyrimidine synthesis

Increased excretion of orotic acid in urine

Symptoms: retarded growth; severe anemia

Only known inherited defect in this pathway (all others would be lethal to fetus)

Treat with uridine/cytidine

IN-CLASS QUESTION: HOW DOES URIDINE AND CYTIDINE ADMINISTRATION WORK TO TREAT OROTIC ACIDURIA?

Orotic Aciduria
degradation of pyrimidines
Degradation of Pyrimidines
  • CMP and UMP degraded to bases similarly to purines
    • Dephosphorylation
    • Deamination
    • Glycosidic bond cleavage
  • Uracil reduced in liver, forming b-alanine
    • Converted to malonyl-CoA  fatty acid synthesis for energy metabolism
deoxyribonucleotide formation
Deoxyribonucleotide Formation
  • Purine/Pyrimidine degradation are the same for ribonucleotides and deoxyribonucleotides
  • Biosynthetic pathways are only for ribonucleotide production
  • Deoxyribonucleotides are synthesized from corresponding ribonucleotides
dna vs rna review
DNA vs. RNA: REVIEW
  • DNA composed of deoxyribonucleotides
  • Ribose sugar in DNA lacks hydroxyl group at 2’ Carbon
  • Uracil doesn’t (normally) appear in DNA
    • Thymine (5-methyluracil) appears instead
formation of deoxyribonucleotides
Formation of Deoxyribonucleotides
  • Reduction of 2’ carbon done via a free radical mechanism catalyzed by “Ribonucleotide Reductases”
    • E. coli RNR reduces ribonucleoside diphosphates (NDPs) to deoxyribonucleoside diphosphates (dNDPs)
      • Two subunits: R1 and R2
        • A Heterotetramer: (R1)2 and (R2)2 in vitro
ribonucleotide reductase
RIBONUCLEOTIDE REDUCTASE
  • R1 SUBUNIT
    • Three allosteric sites
      • Specificity Site
      • Hexamerization site
      • Activity Site
    • Five redox-active –SH groups from cysteines
  • R2 SUBUNIT
    • Tyr 122 radical
    • Binuclear Fe(III) complex
ribonucleotide reductase r2 subunit
Ribonucleotide Reductase R2 Subunit
  • Fe prosthetic group– binuclear, with each Fe octahedrally coordinated
    • Fe’s are bridged by O-2 and carboxyl gp of Glu 115
    • Tyr 122 is close to the Fe(III) complex  stabilization of a tyrosyl free-radical
  • During the overall process, a pair of –SH groups provides the reducing equivalents
    • A protein disulfide group is formed
    • Gets reduced by two other sulfhydryl gps of Cys residues in R1
chime exercise
Chime Exercise

E. coli Ribonucleotide Reductase:

3R1R and 4R1R: R1 subunit

1RIB and 1AV8: R2 subunit

  • Explore 1AV8: Ribonucleotide Reductase in detail.This is the R2 subunit of E. coli Ribonucleotide Reductase.  The biological molecule consists of a heterotetramer of 2 R1 and two R2 chains.
  • Identify the following structures:
    • 8 long -helices in one unit of R2
    • Tyr 122 residue
    • The binuclear Fe (III) complex
    • The ligands of the Fe (III) complex 
mechanism of ribonucleotide reductase reaction
Mechanism of Ribonucleotide Reductase Reaction
  • Free Radical
  • Involvement of multiple –SH groups
  • RR is left with a disulfide group that must be reduced to return to the original enzyme
ribonucleotide reductase63
RIBONUCLEOTIDE REDUCTASE
  • ACTIVITY IS RESPONSIVE TO LEVEL OF CELLULAR NUCLEOTIDES:
    • ATP ACTIVATES REDUCTION OF
      • CDP
      • UDP
    • dTTP
      • INDUCES GDP REDUCTION
      • INHIBITS REDUCTION OF CDP. UDP
    • dATP INHIBITS REDUCTION OF ALL NUCLEOTIDES
    • dGTP
      • STIMULATES ADP REDUCTION
      • INHIBITS CDP,UDP,GDP REDUCTION
ribonucleotide reductase65
RIBONUCLEOTIDE REDUCTASE
  • CATALYTIC ACTIVITY VARIES WITH STATE OF OLIGOMERIZATION:
    • WHEN ATP, dATP, dGTP, dTTP BIND TO SPECIFICITY SITE OF R1 (CATALYTICALLY INACTIVE MONOMER)
      •  CATALYTICALLY ACTIVE (R1)2
    • WHEN dATP OR ATP BIND TO ACTIVITY SITE OF DIMERS
      •  TETRAMER FORMATION
      • (R1)4a (ACTIVE STATE) == (R1)4b (INACTIVE)
    • WHEN ATP BINDS TO HEXAMERIZATION SITE
      •  CATALYTICALLY ACTIVE HEXAMERS (R1)6
thioredoxin
Physiologic reducing agent of RNR

Cys pair can swap H atoms with disulfide formed regenerate original enzyme

Thioredoxin gets oxidized to disulfide

Thioredoxin

Oxidized Thioredoxin gets reduced by NADPH ( final electron acceptor)

mediated by thioredoxin reductase

thymine formation
Thymine Formation
  • Formed by methylating deoxyuridine monophosphate (dUMP)
  • UTP is needed for RNA production, but dUTP not needed for DNA
    • If dUTP produced excessively, would cause substitution errors (dUTP for dTTP)
  • dUTP hydrolyzed by dUTPase

(dUTP diphosphohydrolase) to dUMP  methylated at C5 to form dTMP rephosphorylate to form dTTP

chime exercise dutpase
CHIME EXERCISE: dUTPase
  • 1DUD: Deoxyuridine-5'-Nucleotide Hydrolase in a complex with a bound substrate analog, Deoxyuridine-5'-Diphosphate (dUDP).
  • Explore dUTPase as follows:
    • Find the substrate in its binding site
    • Find C5 on the Uracil group. Is there enough room to attach a methyl group to C5?
    • Locate the ribose 2’ C. What protein group sterically prevents an –OH group from being attached to the 2’ C atom?
    • Find the H-bond donors and acceptors (to the uracil base) from the protein. What would be the effect on the H-bonding if the base was changed to cytosine?
tetrahydrofolate thf
Tetrahydrofolate (THF)
  • Methylation of dUMP catalyzed by thymidylate synthase
    • Cofactor: N5,N10-methylene THF
      • Oxidized to dihydrofolate
  • Only known rxn where net oxidation state of THF changes
  • THF Regeneration:

DHF + NADPH + H+ THF + NADP+(enzyme: dihydrofolate reductase)

THF + Serine  N5,N10-methylene-THF + Glycine

(enzyme: serine hydroxymethyl transferase)

slide70

REGENERATION OF N5,N10 METHYLENETETRAHYDROFOLATE

dUMP

dTMP

thymidylate synthase

DHF

N5,N10 – METHYLENE-THF

NADPH + H+

GLYCINE

dihydrofolate reductase

serine hydroxymethyl

transferase

NADP+

SERINE

THF

slide71

INHIBITORS OF N5,N10 METHYLENETETRAHYDROFOLATE

REGENERATION

dUMP

dTMP

thymidylate synthase

DHF

N5,N10 – METHYLENE-THF

X

NADPH + H+

FdUMP

GLYCINE

dihydrofolate reductase

serine hydroxymethyl

transferase

NADP+

SERINE

X

THF

METHOTREXATE

AMINOPTERIN

TRIMETHOPRIM

anti folate drugs
Anti-Folate Drugs
  • Cancer cells consume dTMP quickly for DNA replication
    • Interfere with thymidylate synthase rxn to decrease dTMP production
      • (fluorodeoxyuridylate – irreversible inhibitor) – also affects rapidly growing normal cells (hair follicles, bone marrow, immune system, intestinal mucosa)
  • Dihydrofolate reductase step can be stopped competitively (DHF analogs)
    • Anti-Folates: Aminopterin, methotrexate, trimethoprim
adenosine deaminase deficiency
ADENOSINE DEAMINASE DEFICIENCY
  • IN PURINE DEGRADATION, ADENOSINE  INOSINE
    • ENZYME IS ADA
  • ADA DEFICIENCY RESULTS IN SCID
    • “SEVERE COMBINED IMMUNODEFICIENCY”
  • SELECTIVELY KILLS LYMPHOCYTES
    • BOTH B- AND T-CELLS
    • MEDIATE MUCH OF IMMUNE RESPONSE
  • ALL KNOWN ADA MUTANTS STRUCTURALLY PERTURB ACTIVE SITE
adenosine deaminase
Adenosine Deaminase

CHIME Exercise: 2ADA

  • Enzyme catalyzing deamination of Adenosine to Inosine
  • a/b barrel domain structure
    • “TIM Barrel” – central barrel structure with 8 twisted parallel b-strands connected by 8 a-helical loops
    • Active site is at bottom of funnel-shaped pocket formed by loops
    • Found in all glycolytic enzymes
    • Found in proteins that bind and transport metabolites
ada deficiency
ADA DEFICIENCY***
  • IN-CLASS QUESTION: EXPLAIN THE BIOCHEMISTRY THAT RESULTS WHEN A PERSON HAS ADA DEFICIENCY
  • (HINT: LYMPHOID TISSUE IS VERY ACTIVE IN DEOXYADENOSINE PHOSPHORYLATION)
ada deficiency76
ADA DEFICIENCY
  • ONE OF FIRST DISEASES TO BE TREATED WITH GENE THERAPY
  • ADA GENE INSERTED INTO LYMPHOCYTES; THEN LYMPHOCYTES RETURNED TO PATIENT
  • PEG-ADA TREATMENTS
    • ACTIVITY LASTS 1-2 WEEKS