Chapter 33 - Metabolism of Purine & Pyrimidine Nucleotides

Question 0

Base component of Inosine Monophosphate (IMP)

Answer 0

Hypoxanthine

Question 1

Genetic disorder of pyrimidine caused by deficiency in dihydropyrimidine dehydrogenase

Answer 1

Beta - hydroxybutyric aciduria / combined uraciluria - thyminuria

Question 2

Function of Nucleosides + example

Answer 2

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

Question 3

Pathway to synthesize more nucleotides that require more steps and enzymes

Answer 3

De Novo Pathway

Question 4

Source of nucleotides that uses preformed nucleosides and bases

Answer 4

Salvage Pathway

Question 5

Pancreatic nuclease that digests DNA?

Answer 5

Deoxyribonuclease

Question 6

Pancreatic nuclease that digests RNA?

Answer 6

riboxynuclease

Question 7

Brushborder enzymes that further breakdown nucleotides?

Answer 7

Nucleosidases

Phosphatases

Question 8

Process that contribute to purine nucleotide biosynthesis (decreasing importance)

Answer 8

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

Question 9

Saan galing ang PRPP (phoshoribose pyrophosphate) + enzyme

Answer 9

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

Question 10

Source of ribose group of both purine and pyrimidine?

Answer 10

PRPP

Question 11

Committed step in the formation of IMP

Answer 11

Glutamine (Glutamyl) PRPP amidotransferase

Question 12

Major site of purine nucleotide biosynthesis

Answer 12

Liver

Question 13

Organs that depends on exogenous purines and why

Answer 13

Brain ( low level of Glutamyl PRPP amidotransferase)

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

Question 14

Overall rate determinant of de novo purine biosynthesis is______?

Answer 14

Concentration of PRPP

Question 15

Inhibits PRPP synthase?

Answer 15

AMP
ADP
GMP
GDP
(via feedback inhibition)

Question 16

Determines rate of PRPP Synthesis?

Answer 16

1. availability ribose 5 phosphorylase

2. activity of PRPP synthase

Question 17

How does AMP inhibit IMP conversion to ATP or GTP?

Answer 17

via inhibition of adenylosuccinate synthase (GTP is also needed)

Question 18

How does GMP inhibit IMP conversion to ATP or GTP?

Answer 18

GMp inhibits IMP deydrogenase

Question 19

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

Answer 19

Lesch-Nyhan Syndrome

Question 20

Symptoms of Lesch-Nyhan syndrome

Answer 20

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

Question 21

When is gout primary?

Answer 21

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

Question 22

Rate limiting step in prokaryote pyrimidine synthase

Answer 22

Aspartate transcarbamoylase

Question 23

Enzyme complex in eukaryotes used in Pyrimidine Synthesis

Answer 23

CAD enzyme complex

Question 24

What is the CAD protein?

Answer 24

Protein used in pyrimidine synthesis which has three uses 1. Carbamoyl phosphate synthetase II 2. Aspartate transcarbamoylase 3. Dihydroorotase

Question 25

Differentiate Carbamoylase Phosphate Synthetase I and II

Answer 25

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)

Question 26

Genetic disorder wherein defective UMP synthase (carbamoyl phosphate)

Answer 26

Orotic aciduria

Question 27

symptoms of orotic aciduria

Answer 27

increased excreted orotic acid anemia mental degradation

Question 28

Negative feedback of carbamoyl phosphate synthase II

Answer 28

UDP | UTP

Question 29

Stimulates carbamoyl phosphate synthase II

Answer 29

PRPP

Question 30

Inhibits aspartate transcarbamoylase

Answer 30

CTP

Question 31

Activates aspartate transcarbamoylase

Answer 31

ATP

Question 32

enzyme for deoxynucleotide biosynthesis

Answer 32

nucleoside diphosphate reductase or ribonucleoside reductase

Question 33

coenzymes for deoxunucleotide synthesis

Answer 33

thioredoxin glutaredoxin NADP

Question 34

What is the end product of purine catabolism

Answer 34

uric acid

Question 35

How does excessive uric acid cause hyperuricemia

Answer 35

excess uric acid becomes prooxidant

Question 36

What would be the effect of a defective adenosine deaminase?

Answer 36

Combined immuno diseases

Question 37

Product of urine catab in: 1. primates, reptiles, birds or insects 2. most mammals 3. bony fishes 4. cartilaginous fish + amphibians 5. marine fishes

Answer 37

1. uric acid 2. allantoin 3. allantoate 4. urea 5. NH4

Question 38

Symptoms of von Gierk's disease

Answer 38

purine overproduction | hyperuricemia

Question 39

Cause of von Gierk's disease

Answer 39

enhanced generation of ribose 5 phosphate

Question 40

enzyme used for purine salvage pathway (hypoxanthine & guanine)

Answer 40

Hypoxanthine-guanine phosphoribosyltransferase

Question 41

enzyme used for purine salvage pathway (adenine)

Answer 41

adenine phosphoribosyltransferase