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Biochemistry > Chapter 33 - Metabolism of Purine & Pyrimidine Nucleotides > Flashcards

Chapter 33 - Metabolism of Purine & Pyrimidine Nucleotides Flashcards

0
Q

Base component of Inosine Monophosphate (IMP)

A

Hypoxanthine

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1
Q

Genetic disorder of pyrimidine caused by deficiency in dihydropyrimidine dehydrogenase

A

Beta - hydroxybutyric aciduria / combined uraciluria - thyminuria

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2
Q

Function of Nucleosides + example

A
  1. Precursors of DNA & RNA
  2. Energy Reservoir ( ATP & GTP)
  3. Cellular secondary messengers ( cAMP, cGMP)
  4. Structural component of coenzymes (SAM, NAD, FAD)
  5. Activated biosynthetic intermediates
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3
Q

Pathway to synthesize more nucleotides that require more steps and enzymes

A

De Novo Pathway

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4
Q

Source of nucleotides that uses preformed nucleosides and bases

A

Salvage Pathway

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5
Q

Pancreatic nuclease that digests DNA?

A

Deoxyribonuclease

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6
Q

Pancreatic nuclease that digests RNA?

A

riboxynuclease

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7
Q

Brushborder enzymes that further breakdown nucleotides?

A

Nucleosidases

Phosphatases

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8
Q

Process that contribute to purine nucleotide biosynthesis (decreasing importance)

A
  1. Synthesis of amphibolic intermediattes
  2. Phophoribosylation of purine
  3. Phosphorylation of purine nucleosides
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9
Q

Saan galing ang PRPP (phoshoribose pyrophosphate) + enzyme

A

Ribose 5 phosphate (using the enzyme Ribose-5-pyrophosphatekinase or PRPP synthase)

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10
Q

Source of ribose group of both purine and pyrimidine?

A

PRPP

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11
Q

Committed step in the formation of IMP

A

Glutamine (Glutamyl) PRPP amidotransferase

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12
Q

Major site of purine nucleotide biosynthesis

A

Liver

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13
Q

Organs that depends on exogenous purines and why

A

Brain ( low level of Glutamyl PRPP amidotransferase)

Erythrocytes and polymorphonuclear leukocytes (does not synthesize 5-phosphoribosylamine)

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14
Q

Overall rate determinant of de novo purine biosynthesis is______?

A

Concentration of PRPP

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15
Q

Inhibits PRPP synthase?

A 
AMP
ADP
GMP
GDP
(via feedback inhibition)
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16
Q

Determines rate of PRPP Synthesis?

A
  1. availability ribose 5 phosphorylase

2. activity of PRPP synthase

17
Q

How does AMP inhibit IMP conversion to ATP or GTP?

A

via inhibition of adenylosuccinate synthase (GTP is also needed)

18
Q

How does GMP inhibit IMP conversion to ATP or GTP?

A

GMp inhibits IMP deydrogenase

19
Q

X-linked disease of Purine metabolism that is characterised by excessive accumulation of uric acid and degradation of the prodcts of purine nucleotides

A

Lesch-Nyhan Syndrome

20
Q

Symptoms of Lesch-Nyhan syndrome

A
  1. high uric acid
  2. self-mutilation
  3. nervous degradation
  4. involuntary movement
21
Q

When is gout primary?

A
  1. Genetic impairment of allosteric inhibition of ribose-5-phosphate pyrophosphate kinase
  2. defect in Hypoxanthine-guanine phosphoribosyltransferase
22
Q

Rate limiting step in prokaryote pyrimidine synthase

A

Aspartate transcarbamoylase

23
Q

Enzyme complex in eukaryotes used in Pyrimidine Synthesis

A

CAD enzyme complex

24
Q

What is the CAD protein?

A

Protein used in pyrimidine synthesis which has three uses

  1. Carbamoyl phosphate synthetase II
  2. Aspartate transcarbamoylase
  3. Dihydroorotase
25
Q

Differentiate Carbamoylase Phosphate Synthetase I and II

A
  1. I (liver only) II (all nucleated cells)
  2. I (mitochondrial) II (cytosol)
  3. I (urea cycle) II ( pyrimidine synthesis)
  4. I ( Ammonium Ion) II ( Amide group of Glutamine)
26
Q

Genetic disorder wherein defective UMP synthase (carbamoyl phosphate)

A

Orotic aciduria

27
Q

symptoms of orotic aciduria

A

increased excreted orotic acid
anemia
mental degradation

28
Q

Negative feedback of carbamoyl phosphate synthase II

A

UDP

UTP

29
Q

Stimulates carbamoyl phosphate synthase II

A

PRPP

30
Q

Inhibits aspartate transcarbamoylase

A

CTP

31
Q

Activates aspartate transcarbamoylase

A

ATP

32
Q

enzyme for deoxynucleotide biosynthesis

A

nucleoside diphosphate reductase or ribonucleoside reductase

33
Q

coenzymes for deoxunucleotide synthesis

A

thioredoxin
glutaredoxin
NADP

34
Q

What is the end product of purine catabolism

A

uric acid

35
Q

How does excessive uric acid cause hyperuricemia

A

excess uric acid becomes prooxidant

36
Q

What would be the effect of a defective adenosine deaminase?

A

Combined immuno diseases

37
Q

Product of urine catab in:

  1. primates, reptiles, birds or insects
  2. most mammals
  3. bony fishes
  4. cartilaginous fish + amphibians
  5. marine fishes
A
  1. uric acid
  2. allantoin
  3. allantoate
  4. urea
  5. NH4
38
Q

Symptoms of von Gierk’s disease

A

purine overproduction

hyperuricemia

39
Q

Cause of von Gierk’s disease

A

enhanced generation of ribose 5 phosphate

40
Q

enzyme used for purine salvage pathway (hypoxanthine & guanine)

A

Hypoxanthine-guanine phosphoribosyltransferase

41
Q

enzyme used for purine salvage pathway (adenine)

A

adenine phosphoribosyltransferase

Biochemistry (4 decks)

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