Peroxisomes
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Most common function of peroxisomes
Fatty acid degradation and reactive oxygen metabolism
Which tissues have peroxisomes
All, most prominent in liver brain and kidney
How many membranes are peroxisomes surrounded by?
One
Do peroxisomes contain DNA?
No
Biological function of peroxisomes
Long branches chain acid shortening (beta and alpha oxidation) Esther lipid plasmalogen biosynthesis Bile acid synthesis Glyxoylate detoxification
Why is long and brbanches chain fatty acid shortening important?
Removing molecules wholes build ip have toxic effects and metabolises some fatty acid based singalling molecules
What happens when glyoxylate isn’t further metabolised?
Oxidises to oxalate which percipitates as a calcium salt resulting in rental failutre
What is beta oxididation consisting of
Sequential remove of 2 carbon units as acetyl CoA
Where does beta oxidation take place?
Peroxisomes and mitochondria
What are the consquences of peroxisome malfunction
Peroxisome biogenesis disorder (Zellweger Syndrome) and single gene deficiency
Steps of peroxisomal protein import
Peroxisomal protein is made in cytosol, binds to receptor PTS1 Receptor docks to protein complex on peroxisome membrane Protein transported into peroxisome Receptor recycled Cycle repeats
In ZS what is defective?
Receptor or components of docking/recycling complexes
Range of names at the Zellweger Spectrum from most severe to least
Zellweger syndrome, Neonatal adrenoleukodystrophy, Infantile refsum disease
Symptoms of RCDP?
Peroxisomes are present but proteins missing. Abnormalities of CNS, overt growth.
Treatment of Zellweger Spectrum Diseases
Symptomatic treatment based on biochemical pathway
What is X-ALD
Disorder of peroxisomal beta oxidation
What gene does X-ALD affect?
ABCD1 gene
What does ABDC1 gene encode?
Membrane protein (ALDP) which belongs to ATP binding cassette family
How is X-ALD diagnosed?
Very long chain fatty acid accumulation
Is there a strong correlation between casual mutation and clinical presentation of X-ALD?
No
What are the most freuqnet presentations of X-ALD?
Childhood cerebral ALD and adrenomyeloneuropathy
When does CCALD (childhood cerebral ALD) manifest
3-10 years
When does adremyeloneuropathy manifest?
Late 20s
Treatment of X-ALD
Adrenal hormone therapy Fat restricted from diet Bone marrow transplant Gene therapy