Aani CP: Protein Catabolism

Question 1

Which enzyme converts hypoxanthine into xanthine?

Answer 1

Xanthine Oxidase

Question 2

Which enzyme converts xanthene into urate (2.6.8 tri-oxypurine)?

Answer 2

Xanthene Oxidase

Question 3

Where is Xanthene Oxidase enzyme found?

Answer 3

Liver and small intestine

Question 4

Which drug inhibits Xanthene Oxidase?

Answer 4

Allopurinol

Question 5

How is azathioprine dose affected by allopurinol?

Answer 5

Azathioprine is broken down by Xanthene Oxidase so Allopurinol rises the dose of Azathioprine.

Question 6

Which enzyme is the rate limiting step in De Novo Purine synthesis?

Answer 6

PAT

Question 7

Which enzyme is the rate limiting step in salvage/recycling of purine synthesis?

Answer 7

HGPRT (Hypoxanthine-guanine phosphoribosyltransferase)

Question 8

A condition in which there is a deficiency in the HGPRT?

Answer 8

Lesch Nyhan Syndrome

Question 9

Describe the pathogenesis of gout in Lesch Nyhan syndrome ?

Answer 9

HGRPT doesnt allow salvage pathway to work so you dont get precursor purines (GMP/IMP) so theres no negative feedback to PAT and it goes into overdrive so you get lots of purine synthesis.

Question 10

Name 3 features of the syndrome above & what is the inheritance?

Answer 10

• Normal at birth
• Self mutilation (1-16 y/o)
• Spasticity
• Learning delay
• X linked (males only)

Question 11

What is gout? Common anatomical site?

Answer 11

Accumulation of monosodium urate crystals

Big toe

Question 12

How to diagnose gout?

Answer 12

Tap effusion. Look at it under polarized light. Will see negatively bifringent needle shaped crystals.
Appear blue
90 degrees to light

Question 13

What is pseudogout? Common anatomical site?

Answer 13

Accumulation of pyrophosphate crystals

Knee

Question 14

How to diagnose peudogout?

Answer 14

Tap effusion. Under polarized light. Positively bifringent crystals, rhomboid shape. In line with light

Question 15

Treatment for acute gout?

Answer 15

1. Anti-inflammatories e.g. corticosteroids/NSAIDs e.g. diclofenac
2. Colchicine
3. Glucocorticoids

Question 16

Another word for chronic gout? Classic anatomical locations?

Answer 16

Tophaecous gout - has tophi

Ears

Question 17

Treatment for chronic gout?

Answer 17

Allopurinol (reduced production of uric acid) or Probenecid (increased excretion of uric acid)
Reduce protein intake
Drink water

Question 18

In Lesch Nyhan Syndrome, which substance is made by De Novo synthesis before it gets converted into uric acid?

Answer 18

Inosinic acid

Question 19

Childhood condition where there is reduced excretion o uric acid?

Answer 19

Familial Juvenille Hyperuricaemic Nephropathy (marked thickening of tubular basement membranes, and leads to progressive renal failure during adulthood)