Purine Salvage Deficiencies

Question 1

Adenosine deaminase deficiency

Answer 1

One of the major causes of autosomal recessive SCID

Excess ATP and dATP imbalances nucleotide pool via feedback inhibition of ribonucleotide reductase –> prevents DNA synthesis and thus decreases lymphocyte count

Question 2

Adenosine deaminase

Answer 2

Enzyme that irreversibly deaminates Adenosine and converts it to Inosine

Question 3

Lesch-Nyhan Syndrome (cause)

Answer 3

Defective purine salvage due to absent HGPRT (hypoxanthine-guanine phosphoribosyltransferase), which converts hypoxanthine to IMP and Guanine to GMP.

Question 4

Lesch-Nyhan Syndrome (findings)

Answer 4

Hyperuricemia
Gout
Pissed off (aggression, self-mutilation)
Retardation (intellecutal disability)
DysTonia

Question 5

Lesch-Nyhan Syndrome (Treatment)

Answer 5

Allopurinol or febuxostat (2nd line)

Question 6

Bases from degraded DNA/RNA

Answer 6

Guanine, Hypoxanthine, Adenine

Question 7

Xanthine Oxidase

Answer 7

Converts Hypoxanthine to Xanthine and Xanthine to Uric acid

Question 8

APRT (adenine phosphoribosyltransferase)

Answer 8

Catalyst in reaction between
Adenine + PRPP –> AMP

Deficiency: rare, but causes kidney stones and nephrolithiasis