Peroxisomes

Question 1

What do peroxisomes do?

Answer 1

fatty acid degradation and reactive oxygen metabolism (common)

Question 2

What are specialised functions of peroxisomes?

Answer 2

part of photorespiration

part of penicillin biosynthesis

glycolysis of trypansomes

Question 3

Which human tissues are peroxisomes present in?

Answer 3

Liver
Brain
Kidney

Question 4

What are the 4 metabolic functions of peroxisomes?

Answer 4

• branched chain fatty acid shortening
• Ether lipid (plasmalogen) biosynthesis
• Bile acid synthesis
• Glyoxylate detoxification

Question 5

What does B-oxidation result in the removal of?

Answer 5

2 carbon units as acetyl CoA

Question 6

Where does B-oxidation take place?

Answer 6

plants - ONLY peroxisomes

Mammals - mitochondria AND peroxisomes

Question 7

What are the 2 consequences of peroxisome malfunction?

Answer 7

• Peroxisome Biogenesis Disorder

- Single Gene deficiency

Question 8

What are Peroxisome Biogenesis Disorders?

Answer 8

failure to assemble the organelle

Zellweger Syndrome spectrum

Question 9

What happens during peroxisomal protein import?

Answer 9

protein binds to PEX5 receptor by PTS1 signal

receptor docks to protein complex on peroxisome membrane

protein transported in

receptor recycled

Question 10

What happens during ZS so that peroxisomal protein import doesn’t happen?

Answer 10

receptor or component of docking/recycling complexes are defective

Question 11

What are the 4 disorders of the Zellweger spectrum?

Answer 11

Zellweger syndrome
Neonatal adrenoleukodystrophy
Infantile Refsum Disease
RCDP

Question 12

How are disorders of the Zellweger spectrum diagnosed?

Answer 12

look at biochemical pathways affected
defective gene undergoes molecular testing
treatment primarily support symptoms

Question 13

What are 2 disorders that arise from mutation in specific enzyme activity within peroxisomes?

Answer 13

X-ALD

PH1

Question 14

What is X-ALD

Answer 14

affect boys - inherit from mother

disorder of peroxisomal beta oxidation

Question 15

What gene is involved in X-ALD?

Answer 15

ABCD1 gene

encodes membrane protein ALDP which belonds to ATP binding Cassette - transports long fatty acid chains into peroxisomes

Question 16

How can X-ALD be diagnosed?

Answer 16

accumulation of very long chain fatty acids

Question 17

What are the symptoms of CCALD (X-ALD)?

Answer 17

inflammatory demyelination of neurones in brain

death within 3 years

Question 18

What are the symptoms of AMN (X-ALD)?

Answer 18

slower progressing
muscle weakness
impaired adrenocortical function

Question 19

What are treatments of X-ALD?

Answer 19

adrenal hormone therapy
diet - restricted fat
Bone marrow transplant (high risk)
Gene therapy

Question 20

What is PH1?

Answer 20

single gene disorder
autosomal recessive condition
defects in Alanine Glyoxylate Transferase (peroxisomal liver enzyme)

Question 21

What does AGT enzyme in the peroxisome do?

Answer 21

converts glyoxylate to glycine

Question 22

What can PH1 be caused by?

Answer 22

No AGT at all

OR

AGT mis-targeting to mitochondria by 2 mutations changing the aa’s

Question 23

What are treatments of PH1?

Answer 23

high dose vitamin B6
avoid foods with high oxalate
liver transplant
kidney transplant

Question 24

What plant fungi diseases are peroxisomes essential for?

Answer 24

rice blast fungus
Anthracnose fungi

produce appressoria with melanised walls