Peroxisomes

role of peroxisomes

many diff metabolic activities tht dep on organism, tissue, development stage and environ conditions

FA degredation adn Reactive oxygen metabolism common to most peroxisomes

where are peroxisomes found

most tissues but a lot in liver brain and kidney

How do peroxisomes shorten branched FA chains

alpha and beta oxidation

Metabolic functions of peroxisomes

shorten FA chains (a and b oxidation)

Ether lipid (plasmalogen) biosynthesis (many in nervous tissue memb)

Bile acid synth (aid lipid digestion and abs of lipid sol vitamins)

glyoxylate detoxification (if not metab its ox to oxalate which ppt. as calcium oxalate cause renal failure)

site of b oxidation

long branched FA chains in peroxisomes then sent to mito when less than or 16 C long for further b oxidation

steps of beta oxidation

oxidation, hydration, oxiation, thiolysis in both mito and peroxisomes

differ in first ox enzyme FAD linked dehydrogenase in mito and FAD linked oxidase in peroxisome (prod O2 that forms H2O2) both prod e for ETC and NADH

Peroxisome biogenesis disorder

failure of multiple perox metabolic pathways due to failure to assemle peroxisomes

Zellweger syndrome spectrum

peroxisomal protein import

peroxisomal protein binds receptor (PEX5), docks on to complex on perox memb and transp in

receptor recycled

how is peroxisomal protein import affect in peroxisome biogenesis disorders (dont form perox)

remain in cyto

In Zellweger syndrome spectrum causes

defective or absent receptor

receptor cant dock on memb so cant import

receptor cant be recycled so import stops

why are peroxisomal proteins not or less effective in zellweger syndrome spectrum

not in right conditions in cyto therefore affect function or may be degraded

disorders of peroxisome function

mut in genes encoding peroxisome enzyme

X-ALD

affect memb protein (ALDP) req for tranp of vlc FAs into perox therefore accumulate (toxic affects)

PH1

defects in Alanine glyoxylate amino transferase (perox liver enzyme)

conv glyoxylate to glycine (accumulates if mut and forms oxalate) b

oxalate binds ca2+ and ppt to cause renal failure

(most lack the enzyme completely, some have mislocalised to mito mito targeting signal or form that is readily imported into mito)