Purine Degradation and Pyrimidine Metabolism 🧬

Question 1

Orotate Phosphoribosyl-transferase

Answer 1

Enzyme involved in the synthesis of pyrimidines

Question 2

dTMP

Answer 2

Deoxynucleotide used exclusively for DNA synthesis, requiring methylene tetrahydrofolate

Question 3

Purine Degradation

Answer 3

Process involving the breakdown of purine nucleotides to uric acid, leading to the formation of end products like hypoxanthine and guanine.

Question 4

Thiopurine Methyltransferase (TMPT)

Answer 4

Inactivates thiopurine drugs, suppressing the immune system; variations in TMPT gene activity can affect drug metabolism.

Question 5

Pyrimidine biosynthesis defect

Answer 5

Results in orotic aciduria and can be differentiated from Urea cycle defect by examining blood ammonia levels

Question 6

Folate

Answer 6

Essential for DNA synthesis during S phase, deficiency leads to macrocytic anemia and decreased cell division

Question 7

Pyrimidine salvage

Answer 7

Process where pyrimidine bases are recycled into nucleotides via PRPP

Question 8

Pyrimidine Biosynthesis

Answer 8

A pathway that involves the synthesis of UTP and CTP, distinguished from purine biosynthetic pathways.

Question 9

Allopurinol

Answer 9

Inhibits Xanthine oxidase, leading to the formation of hypoxanthine & xanthine, which are more soluble than uric acid.

Question 10

Gout

Answer 10

Hyperuricemia: underexcretion of uric acid deposition of monosodium urate crystals = recurrent attacks of acute arthritic joint inflammation.

Question 11

Orotic aciduria

Answer 11

A condition characterized by macrocytic anemia, resistance to usual therapies, and abnormal height and weight in infants

Question 12

Uridine

Answer 12

Improves anemia by serving as a precursor for thymidine and cytidine synthesis

Question 13

5-Fluorouracil

Answer 13

Anticancer drug that irreversibly binds thymidylate synthase, inhibiting DNA synthesis

Question 14

Uric Acid

Answer 14

End product of purine breakdown, can lead to hyperuricemia and gout if levels are elevated.

Question 15

Regulation of Pyrimidine Biosynthesis

Answer 15

Involves regulatory enzymes and regulators that control the synthesis of pyrimidines within cells.

Question 16

Purine Nucleoside Phosphorylase Deficiency (PNP)

Answer 16

Autosomal recessive disorder that is less severe than ADA, causing recurrent infections and neurodevelopmental delay.

Question 17

Deoxyribonucleotides

Answer 17

Formed from ribonucleotides through a process that requires specific coenzymes and inhibitors, crucial for DNA synthesis.

Question 18

Adenosine Deaminase Deficiency (ADA)

Answer 18

Autosomal recessive cause of severe combined immunodeficiency (SCID) where untreated children usually die before 2 years from overwhelming infection.

Question 19

Orotic acid levels

Answer 19

Deficiency leads to decreased RBC formation, megaloblastic anemia, and reduced DNA synthesis